In my experience, students love creating word clouds using Wordle. It's pretty simple to use and students can change size, fonts, and colors to fit their preference.
At first 100 people to follow seemed outrageous! :) It was really easy to get there though and I'm pretty excited to start using it more often. I jumped on the twitter bandwagon a while back, when it first became popular, but never did anything with it.
I was always a little apprehensive to start a blog, but it really was easier then expected. It would be fun to have students start a blog at the beginning of the year and see how it develops throughout the year. I also now feel more comfortable starting my own blog for parent communication.