One of my colleagues showed me this website, and it was so much fun, I had to share it!
Corkboard.me is a shareable bulletin board that allows anyone to put up post-it notes. The website will give you a link that will be your own personal corkboard. You can share the link, or embed it into a website. I did notice that it didn't work well with IE7, but worked perfectly with Firefox.
I linked it into our Moodle LMS, and thought it looked good (see image). I'm thinking of using it to remind students about coming exams, filling out their evaluations, and letting them know about new additions on the coursepage. The students can also create one, and post reminders about the team projects, or just a 'quote of the day' for some social interaction.