Which Wiki is Right for Me?

Shonda Brisco is one of the most techie librarians I know. Well, I don't personally know her since she is in Texas and I am in Pennsylvania, I virtually know her from my great library list-serve LM_Net. She wrote a wonderful article for School Library Journal about choosing the right Wiki. Since I am interested in starting a Wiki, I loved it. If you are just starting out with Wikis, maybe you would like it too. I think my favorite Wiki for elementary students is pbWiki and I want to introduce it to my students next year. So, I will be playing with it quite a bit this summer. What is your favorite Wiki?