Blogs, journals, online communities

MCL Teens: Teen Council Blog: http://teens.multcolib.org/blog/
All Girl Army: http://allgirlarmy.org/

"A blogger collective."
Flickr: http://flickr.com

Post, organize, and share your photos.
Last.fm: http://last.fm

Tell Last.fm your favorite songs. It'll create a custom online radio station for you. The more songs you rate, the better it gets at recommending new songs.
LibraryThing: http://www.librarything.com/

Enter just your favorite books or your whole library, see what others are reading, and more!
Takkle: http://www.takkle.com

"TAKKLE is the social network for high school sports...post photos and videos, share stats and schedules, and a whole lot more with others throughout the TAKKLE community."