I've talked before about Google Apps Education Edition with respect to student email addresses, but I wanted to revisit the other things that are included with this. Hopefully without sounding too much like a commercial.
Create, Edit, and Share Documents
Google Docs is like an online Office Suite. It includes a word processor, as well as spreadsheet and presentation programs. I've used it for student assignments (both that I assign and that they submit) and for sharing lab data amoung the students. Not quite as many features as Microsoft Office, but available from any computer with an Internet connection.
The interface of Google calendar is, imho, better than any other calendar software I've used. It also allows for private, public, and shared calendars. I've used it for class test schedule reminders (embedded in my website) as well as for staff supervision scheduling. You can even integrate your calendar with out district's mandated school site. And it syncronizes with my iPod Touch.
Quick and easy way to create feature-rich websites for your domain, of which my website is an example. Teams, clubs, and even individual students can create "sites" if it is enabled.
All of these features, and a few that I haven't mentioned, can be enabled or disabled as you see fit. Google Apps Education Edition is not without its shortcomings, as I've mentioned, but I do have to say that I'm a big fan.