Posterous, which is on The Best Places Where Students Can Write Online list, has just added the ability to write group blogs.  The key attribute that Posterous has is that you can add blog posts by email.

You can read more about it at TechCrunch.

I’ve found Posterous to be a decent option for students to display their online work, though I believe Edublogs is still the place to go if you want students to do serious writing and communicate with others.