Given the time it takes to moderate communities well, finding volunteers to do that for free is not likely. It is better to hire a community manager who already has experience who is willing to keep growing as communities change.

Reddit is a perfect example of a community that businesses would probably want to avoid. Why is explained in http://www.dirjournal.com/articles/reddit-guide-how-to-use-reddit/

Each community is different and requires different skills, tools, and strategies. Here are some you may find beneficial:

These posts explain the currently available tools for managing Instagram communities http://www.socialmediaexaminer.com/instagram-community/
http://www.ignitesocialmedia.com/community-management/instagram-direct-means-community-managers/
http://www.razorsocial.com/instagram-tools-to-grow-your-presence/

Tips for using Snapchat
http://socialmediatoday.com/amy-birch/1402306/how-use-snapchat-part-your-marketing-strategy

Strategies for Vine
http://blog.360i.com/360i-news/5-best-practices-for-brands-using-vine

There is a Google Plus Community Manager group where you can find discussions and strategies: https://plus.google.com/communities/101510889779807726729

You can find many more tips online such as Mashable's 12 Top Community Managers Share Their Tips for Better Engagement http://mashable.com/2012/03/15/community-manager-engagement-tips/

I hope these cover what you really wanted to know. We would need more specifics (platform, business, goals) to answer more clearly.

Have you considered identifying groups they are involved in and asking them through that group? There could be a Facebook group for their University or possibly even a Google + Community? Facebook ads can be targeted by many factors, and a university might be one of them. (You'd have to consult an expert on Facebook advertising to find out. I am not one, but I may know others who can tell me.)

Also search LinkedIn for groups related to specific universities. You can often join such groups and interact yourself or you can identify leaders and contact them to ask whether they would be willing to tell the group about your test.

You could also consider advertising in the school paper. Most Universities would have one which you could find by typing in "University paper" in any search engine or by using specific university names in your search, i.e.: "Yale University paper", "USC university paper", etc.

Other ways you could find students are local free classifieds such as Thrifty Nickel, Pennysaver, etc. or by posting on Craigslist.

You could also create something so entertaining it would go viral to reach them (often done in conjunction with Facebook), but that can be a major challenge not easily done without a substantial budget.

Tom Williams has the best idea though - in person outreach in the manner he described will work best. I went ahead and shared these other ideas because I suspect you want to do many campuses and may not have the budget to travel to them all.

Here are examples of some of the top brands who write about content marketing. Obviously, they should be creating the type of content you ask about because it is their specialty.

MarketingProfs / http://www.mpdailyfix.com/
HubSpot / http://blog.hubspot.com/
KissMetrics / http://blog.kissmetrics.com/

Content Marketing Institute has two longer lists of Top Content Marketing Blogs at http://contentmarketinginstitute.com/top-content-marketing-blogs/ and http://contentmarketinginstitute.com/2011/06/content-marketing-experts-blog-list/

The number one thing common to top content is that it is written by a subject matter expert - what many have taken to calling a "thought leader". There are many writers capable of researching a topic and writing a compilation, but only someone who truly knows the subject writes the type of content that gets highly shared and frequently garners links.

I can provide assistance identifying and contacting such writers, but I suspect that what you really need is higher visibility which comes from having information about your start-up published on major sites in addition to on your own.

This is the type of blog outreach I am working on most often: providing influential writers with everything they need to write excellent content about a brand which they can get published on sites for which they already write.

If you would like me to show you the tools we use to make that happen feel free to contact me.

Identify (or hire) a team member you can train who is as adept at training others as you are (or even moreso). Teach this person so that you can delegate much of the time-consuming one-on-one training to them (and so there are at least two people who know all the processes necessary to keep your start-up running).

Have this person document processes. One excellent inexpensive way to do that is using Screencast-o-matic http://www.screencast-o-matic.com/ to create short videos on how to do specific tasks.

I recommend using Trello http://trello.com as the fast, easy way to collaborate across a team. Create ongoing processes as lists on boards there and then move the tasks from list to list to show where each task is in your process. This is easier explained using screen sharing on Skype or by watching videos on how Trello works. It is extremely simple to set-up, use and learn.

By setting up Trello boards you can instantly see what team members are focusing on and what they've accomplished so far at a glance. You can set deadlines and import them into a calendar visible to all team members or just you. I highly recommend using Trello as the best collaborative solution available. You'll like the price: free until you need advanced options or want more granular control of who can do what.

I haven't personally used one, but try searching for affiliate job board widget. Monster has one at http://publisher.monster.com/Widgets/ for their affiliate publishers. See these links:
http://publisher.monster.com/
http://publisher.monster.com/Widgets/Job-Board-Widget.aspx

There are others. Either search for affiliate on major job boards, or do the search I suggested. You can also see these widgets that came up for a search on widgetbox for jobs: http://www.widgetbox.com/search?q=jobs

The key thing to know is that you want an affiliate plugin or widget provided by a major job board that has many listings. It would make sense for LinkedIn to have an affiliate offering for their jobs listings; however, I haven't found information on it yet. If I don't find it fast enough I won't be able to edit this answer to include it. You can contact me for more details on these.

If you find one you like or need additional information I can ask our Blogger Mastermind group if anyone has used any of these or can recommend others. We have 100+ serious bloggers who are likely to have more suggestions.

The primary reason someone originally follows you is because you followed them, so your first task is to seek out those interested in what you share and follow them. Retweet what you find most interesting of what they've shared. Interact with them. That is why it is called "social" media.

If you don't tweet at least once a month anyone doing Twitter seriously may unfollow you. Consider feeding content that is most interesting to your followers. Usually that would be similar to what you tweet about, but produced by others. One way to do that is explained in How to Use Twitterfeed http://growmap.com/how-to-use-twitterfeed

There are tips, how-tos, strategies and videos for anyone from beginners to advanced Twitter users at http://growmap.com/twitter-best-practices

If you would like one-on-one training or assistance in learning or setting up any of these strategies give me a call.

It is unlikely that others will want to write content on a brand new blog. Typically, the blogger must create quality content for a specific topic and build an audience first, and only after that will others be willing to write guest content for you.

There are 12+ million established blogs and probably 30+ million installed blogs. There is almost no benefit to other writers to spend time writing for your site. They are much better off writing on established sites or creating their own authority content.

Identify why freelancers would be willing to join a paid community when there are so many free communities already available to them. In order to get people to join and stay they must know what value you can bring that they can't get elsewhere without paying.

It is difficult to keep people active even in free communities. Charging them for the privilege is a tougher challenge. Either way, it is typically the leader(s) who keep things going. In every group I've ever joined or started when I stopped driving the bus the groups faded and died.

You may be, hire, or partner with strong leaders who become a major attraction. Freelancing is very broad, so unless you bring on other experts you might consider narrowing your focus to a specific type of freelancing skill or at least start out in a particular industry.

Your question indicates that you actually have more than one issue:

1) Feeling guilty when you're not working.
2) Being unable to scale yourself.

You must give yourself permission to take time away or you will feel burnt out. While a strong work ethic is essential to success, working constantly is counter-productive. Schedule time off on your calendar and take it. You will find you get just as much done because you will be more focused when you're working.

Service businesses can be scaled by collaborating with others who can take some of the workload. Plug into our collaboration so you can meet other entrepreneurs who can take on work you aren't as qualified to do or cover for you so you can take time off or in emergencies. We share workloads to smooth out the feast or famine issues that come from being a small freelancer.

Working with others will free up time so that you can implement the excellent advice offered by Laura Lee Rose. If you're already working too much you will need to prioritize and delegate (or turn away work that is not a good fit) so that you can create ways to increase your income in fewer hours.

If you would like to see our collaboration and find out how it works feel free to contact me.

Sending a smaller list multiple emails in a series (NOT the same piece multiple times) will work best. I would definitely not keep sending exactly the same email as almost anyone who actually opened more than one would consider that spamming.