I wanted to point out that Tadalist.com is no longer available. Since I have 28 students in my class, I wanted to have 7 groups of 4 so I needed to come up with multiple new resources. Here's what I have.
Group 1 - Social Bookmarking: delicious.com
Group 2 - Word Cloud: wordle.net
Group 3 - List Creation: rememberthemilk.com
Group 4 - Social Bookmarking: stumbleupon.com
Group 5 - Word Cloud: tagxedo.com
Group 6 - List Creation: wunderlist.com
Group 7 - Social Bookmarking: diigo.com
Hope this helps!