Web 2.0 Reviewed

I have been looking into more Web 2.0 applications and one drawback I see is the issue of having so many login names and passwords. Using these in the classroom with many students may end up creating management issues. I have also noticed some are not edited or restricted which would not work in the school setting. The main issue I see right now is finding a good site that has some monitoring and one that will not over fill your inbox with lots of junk email. I am still looking for a good site.