I've been setting up Gaggle.net accounts for students and teachers at a school I am working with. This service is free, although they do have banner ads on all pages and pop-ups from time to time. So far, we've brought the 5th to 8th graders online and they have proven to be able to ignore the ads. This service allows us to limit who the students can write to and who can write to them. It screens for bad language. It also allows the teacher to view any mail to or from students under his or her care.

Teachers have to deal with all blocked mail allowing it to go through or stopping it. Right now we are set so they can only write to people within the school. The only problem we've had so far is that the kids aren't careful with spelling and so mail looks like it's going to someone not in the system and gets blocked.

Very cool system!