I hadn't planned on using any web sites but somehow stumbled across this one when I was searching for information on probes and global positioning systems. http://www.superkids.com is worth mentioning. While it does contain links to Amazon Books and software purchases(don't care for the commercial aspect), it does have something to offer the classroom teacher. It is an educational software review site. It includes articles about unintentional pornography using search engines, the impact of class size, and how to prepare for the SAT.
Also included are tech support links, games, and a famous quote of the day. You can find a vocabulary word of the day for lower, middle, and upper grade levels. It has math worksheets you can create easily specifying level and concept. Best selling and award winning books are easily found for all age levels.
It has a few links for kids and parents, more for teachers(most I'm not familiar with- did like the looks of the 50 states facts site- http://www.ice.net/~edbear/USfacts.html) . Among the parent links is a family friendly search engine:
Other old favorites:
http://school.discovery.com/ (great lessons and news info under earthalert)