While I can't think of much locally which is done online, there are numerous global efforts which you could contribute to. Take a look at
http://forums.whyweprotest.net/index.php - in particular the Online Activism section - and see if there's anything there you feel you can help with, or improve.
While I believe most of this has been done, you could also take a look at
Project ReMedial, and see if there is anything mentioned there (and not yet done) that you could help with, or even any other ideas you have for the project.
Just a couple of ideas off the top of my head, I'm sure there're others people will chime in with.