Best free educational websites I've used, so far:
As a homeschooling mom, I want the time my kids spend online to be educational as well as safe, fun, and engaging.
These are sites my son (five) and I use and we both love:
http://www.timeforkids.com/around-the-world (world culture; people/places),
http://artpad.art.com/artpad/painter/ (painting online),
http://www.dickblick.com/lesson-plans/ (art projects),
http://kids.nationalgeographic.com/kids/animals/ (facts, sounds, and videos of animals),
http://www.montereybayaquarium.org/ has podcasts from the aquarium and activities,
http://news.discovery.com/ (current science and history facts)
or for lesson plans: http://www.discoveryeducation.com/search/page/k-5/science/-/-/index.cfm,
http://www.sfskids.org/ (from the San Fransisco Symphony, fun learning about music),
http://virtualology.com/ (awesome online library for science, art, & history),
and of course http://pbskids.org/ (for educational games).
More on internet safety for kids here.
My son loves http://readingeggs.com/, though it's not free. It really taught him to read in a very short time! Once it got more difficult he wasn't playing it so much, so we took a break. But now he's back at it and wants to play daily. I recommend taking advantage of the free trial! And there are discount codes you can get before purchasing if you want to continue.
There is a free app for your smartphone you can get! Eggy Words App. There are some other new apps as well, such as one for Spelling.
If you're a homeschooling family in Santa Cruz county, join us on Facebook at http://www.facebook.com/groups/HomeCruzers/ for park days, hikes, field trips, friends, support, mom's night out, and more!
Also, these sites were recommended by some of my homeschooling mom friends and I can't wait to try them out with my kids:
What are your favorite educational sites?