Geni.com is neat.
A great option for dealing with complicated family relationships in history or novels (Richard III for instance). Have your students plot out the family tree and upload pictures all for free in a very easy ajaxy environment. You can move around and zoom in and out to get the big picture.
It allows multiple authors so it’s great for group projects and it also has a list view which might be better for some learners. It’s also searchable and you can easily add pictures.
The negatives seem to be that you need to have an email address to use it and to invite others in as well. I can’t figure out a way to share a link with non-invited users as of yet either.
All in all really cool and I heard about it on Net@Night.