Search Engines 

Ask Jeeves For Kids
Ask Jeeves is a unique service where you enter a question, and Ask Jeeves tries to point you to the right web page that provides an answer. At Ask Jeeves For Kids, answers have been vetted for appropriateness. Also, if Ask Jeeves cannot answer a question, it pulls results from various search engines in its metacrawler mode. At Ask Jeeves For Kids, no site that is on SurfWatch's block list will be listed.

Yahooligans
Yahoo for kids, designed for ages 7 to 12. Sites are hand-picked to be appropriate for children. Also, unlike normal Yahoo, searches will not be forwarded to Yahoo's search engine partner Inktomi if there is no match from within the Yahooligan listings. This prevents possibly objectionable sites from slipping onto the screen. Additionally, adult-oriented banner advertising will not appear within the service. Yahooligans is the oldest major directory for children, launched in March 1996.

KidsClick!
Backed by librarians, KidsClick lists about 5,000 web sites in various categories.

These search engines are for older students or adults, as the content is not filtered.

Google
This is my favorite.  You can put in a question, an error message or a single word and it will find good information

Yahoo
http://www.yahoo.com

Ask Jeeves
http://www.askjeeves.com

Dogpile
http://www.dogpile.com