I also like this site. It has a lot of great ideas if you are just starting out with students having some online discussions. It can be hard for me to make sure they are heading in the right direction, if one is necessary, without me guiding them to the outcome. It can also be great if you want a general, but good discussion, it can help with boundaries.

I like this as an alternative to Powerpoint. The students can collaborate on slides, and they can work on them from home. This has made a big difference in the quality of the presentations. They also enjoy not being restricted to the limited class time to work.