Julie and some others were asking today about the ethics of blogging with kids. I've blogged with kids before, with great success, and I intend to blog with them in the future. (Hmm ... I've never conjugated the word "blog" before -- but it's kind of fun!)
Anyway, if you're going to blog with students, which is still a rather gray area in a lot of places, it's probably a good idea to involve your administrators and parents. I'm sure you knew this already, but better safe than sorry. I've got a wiki where there's lots of stuff that might be useful to you in terms of sample policies, permission slips, student activities and other handouts and conversations.
Check through the links and see what's useful. If you need something that you can't find on the wiki, let me know and I'll track it down for you.
Better yet, go ahead and create what you need and then share it with us on the wiki.