KID-FRIENDLY:

Discovery School Tools to help you study, games to challenge your mind, and learning adventures
Enchanted Learning Educational web sites and games for PreK - 6. Search by category or keyword
Fact Monster Reference materials, fun facts and features, and individualized homework help
KidsClick! Age appropriate web sites chosen by librarians. Well-organized, reading levels, no advertising
Kid Info Organized according to curriculum covered in elementary school
KidsKonnect Excellent site created and maintained by educators
Yahooligans Search by categories or keyword.  Commercial

700+ Best sites for kids Chosen by the American Library Association
Ask Jeeves for Kids Natural language searches and reference help
Bigchalk Study and research help
Homework Spot Links for study and research, activities, interactive field trips
KidsConnect A question-answering, help and referral service to K–12
Lycos Zone Easy to use, colorful. Commercial

FOR EVERYONE:

Google Very current, lots of results
About.Com Sites selected by people
AskJeeves Natural language searching
Awesome Library 15,000 reviewed resources, including the top 5 percent in education
DeweyBrowse Organized by Dewey Decimal numbers
Librarian's Index to the Internet No frills, easy to use.  Created by the Library of California)
Yahoo Narrows searches by categories

OTHER GENERAL SEARCH ENGINES:
Alta Vista
Excite
InfoSeek
Lycos
Northernlight
Oingo