Note: Bear with me, I'm starting to organize my learning links on this tab. I'm also checking to see which are still active. As I find the time, I will transfer all of my learning links here for my convenience. Oh! You can use them, too.
General
Ask Kids - A search engine for children.
BrainBashers - A collection of logic games and puzzles. The main page includes an odd word of the day and featured fun sites.
BrainPop - Cartoons featuring Moby the Robot covering various topics across many subjects. You need a membership to use the entire site, but there are plenty of free videos featured to offer supplemental learning.
Free Rice - Various quizzes on basic math, chemistry symbols, English grammar and vocabulary, foreign languages, literature, art, and geography. Test your knowledge and help end world hunger!
Random Facts - A collection of lists of facts on various topics, including history, animals, people, health, etc. PG warning! You may want to review some lists before showing them to your kids.
Museum Sites
Exploratorium - Science, art, and human perception
MetMedia - Metropolitan Museum of Art exhibits presented through multimedia. Includes a kids' zone of child friendly media.
Ology - American Museum of Natural History's science site for kids. Neat experiments!
Young Explorers - Kids' page for the British Museum (I also highly recommend the museum's main site)
Math
Khan Academy - Great videos for helping with math and physics.
Science - General and Labs
Integrated Science at Home - Offers science experiments you can do at home, along with links to the family's other science blogs.
ScienceHack - A search engine for links to various science videos.
Zooniverse- Various real science possibilities, including Planethunters, where citizen scientists help identify possible planets in Kepler light curves.
Science - Biology
eBird - Cornell Lab of Ornithology site that offers participation in citizen science programs like Project Feeder Watch and the annual Great Backyard Bird Count.
Animal Diversity Web - Gives information on animals including pictures and species classifications.
Monterey Bay Aquarium Web Cams - Observe various animals at the aquarium.
Peep Research - Mock experiments using Peeps marshmallows. (demonstrates scientific method)
What's Bugging You? - Entomologist Dr. Art Evans' blog.
BugGuide.Net - A bug identification resource.
WhatBird.com - A bird identification resource.
Science - Physics
The Physics of Superheroes - Website for the book. It includes videos of some of the professor's lectures.
Science - Earth Science and Astronomy
Cosmic Quest - Teaches how astronauts survive in space.
History and Geography
digNubia - A site exploring history and archeology. Requires Flash for some content.