Here is how I search for the .edu links. This helped some of my sites tremendously. I moved couple of the sites for highly competitive keywords from 30th to top 10 position in Google.
So let me know how it works for you.
site:edu inurl:login (Register an account)
site:edu "powered by vbulletin"
inurl:.edu/ (Powered by Invision Power Board)
site:edu "powered by SMF"
My recommendation is to not overdo it.Register the account, put your link in footer and don't spam. Post few posts and then move on to the new one.