You can look for .edu and .gov blog and forum and try to be active in the community, you can get some bcklink from there with your comment and thread. Otherwise, you can go for paid links.
Some edu's and gov's have forums. If so, you can include a link in your signature or profile, that should count as a backlink.
take a look at here http://forums.digitalpoint.com/showthread.php?t=547770 it has some .edu but PR had reduces.
You could start your own EDU blog....its not the PR8 university I offer, but its a start: http://stemmed.sagrado.edu/wp-signup.php
It is a seo tool that tells how many inbound link you are getting to your website from Google. The more high page rank backlinks from authority sites the better.
i think , you should get a lot baclklink from .edu or gov _________________________________________________________________________________________________________________________________
I get quite a few .edu (also .au and .uk edu) backlinks but that's just because I have a site that is worth linking to from a .edu site. I never asked anyone to do it, it just happened.
I don't think .edu domain backlinks will be useful for the ranking, it is the same as all domain links
.edu and .gov back links are more helps to your sites, you can join community of blog and forum and try it.
I do not think so it is free. First you need to buy or if you have a good content which can be useful to college students then you can contact that particular university and can share your content with those site....
if any of you have the list of this .edu and .gov forums and blogs please post it here, it would be helpful