Recommended sites:

Fact Monster - A lot of facts

FirstGov.gov - Official U.S. Government Web Portal

Who2? - Find famous people

Dictionary Sites:

One Look Dictionary - Provides results from multiple online dictionaries

Etymology Dictionary - Word origins

Synonyms & Antonyms

Other good sites:

Ask Jeeves

Yahooligans

KidsClick!

Internet Public Library

Awesome Library

Great Sites

KartOO - Visual Meta Search Engine

Educator's Reference Desk

ERIC - Education Resources Information Center

INFOMINE - Scholarly Internet Resource Collections