What age kiddoes are you doing the wikis with?
I used wikispaces - and I got the free education upgrade so that only
those invited can see it and participate.
The students don't need e-mail accounts and if you create user names and
passwords, the site will set it all up for you.
We have started using it this weekend - I can also get e-mail updates so
I know when a student has added something to the page - I created pages
for my art/writing class... not only do the students have to add right
now - they have to give some feedback to at least two students -