Christmas Fun Online...
http://www.noradsanta.org/en/index.html - This has a little Santa Village and each day they add a new game. My seven year old loves the games. I lost track of how long he was on this site yesterday and I am sure it was over an hour - bad mommy! Anyhow on Christmas Eve they will start tracking Santa's team. Here is the direct link to the village with the games http://www.noradsanta.org/en/countdown.html
http://www.northpole.com/ - You can get printables here, send santa a letter (and he will write back), do crafts, and lots more. There is even a place for teachers and homeschoolers.
Here are two games my three year old enjoyed:
Christmas Bells: Make music with the Christmas bellsDress Up Elves: Two little elves to dress up for Christmas. (Flash)
SHHHH....This is one for your eyes only...
You can take a picture of your living room, upload it to the site, and then add a santa. Show it to your kids Christmas AM so they know Santa was there. This one is not free... but for 9.95
http://portablenorthpole.tv/ This site asks you a few questions about your child and then produces an adorable video where Santa personally welcomes your child, congratulates him/her for being well behaved and hints at what special treat might be under the tree Christmas morning. It's the personalized Santa Claus letter for the digital generation. I just did one for my kids and it turned out so cute. Make sure you upload a picture of your child.