INTERNET SEARCH ENGINES FOR KIDS
DuckDuckGo: Search engine with less spam results and clutter
Safe Search Kids: A kid safe search engine in conjunction with Google.com

GENERAL HOMEWORK HELP
Fact Monster: a free reference site for students, teachers, and parents. Get homework help and find facts on thousands of subjects
Khan Academy: Video Library, practice exercises, and assessments for many topics including math and science, for all ages.