As I mentioned on the SBISD Library Wiki, I think a parent- and teacher-used Wiki would be great for planning field trips. Times, dates, supplies, and parent chaperones could all be coordinated on one page, for all the users to see.
Also, a student-centered Wiki would be great for test preparation. Students could post about concepts they weren't quite clear on, and other students could explain it in their posts. I think the online medium for this would give both those who are struggling, and those who are excelling, a little more confidence to admit it. It would also foster a sense of community among classmates, since they'd be helping each other out, and learning from each other.