Here are some of my favorite links for kid stuff!
http://pbskids.org/ games for the younger ones!
http://www.starfall.com/ great for learning to read and phonics!
http://www.spellingcity.com/ Make or choose spelling lists for your kids to practice at home. Sweet Pea's favorite spelling city game is "hang mouse". It's like hangman except when you've guessed too many wrong answers the cat catches the mouse (but doesn't eat it).
http://girlgames1.com/ Games for girls (imagine that!), my school-agers are able to play most these games, but the younger one's struggle with most of them. Watch them on this one though, many of the games are fine but I don't like some of them.
http://funshineexpress.com/ I order my preschool curriculum from them, they have suppliments that can be used by anyone as well.
http://www.first-school.ws/INDEX.HTM One of the many websites I use to suppliment my curriculum.
http://www.abcteach.com/index.html This website is vast and I can spend hours looking through it for fun and educational worksheets!
http://www.perpetualpreschool.com/ This is basically a compilation of a TON of ideas from teachers, organized by theme.
http://www.edhelper.com/K3Themes.htm Yet another website I use to suppliment preschool themes.
http://www.zerotothree.org/ Great resource for parents of young children.
http://www.dltk-kids.com/ Printable crafts for young children.
http://www.coloring.ws/coloring.html You guessed it, free coloring pages.
http://www.sciencebob.com/index.php Really cool science website for kids of all ages!
There you have it! Do you have any to add to the list?