This is a great place to start genealogy and to keep track of your family tree. There's also an option to do an ancestry DNA test, which is pretty dang cool.
Run by the LDS, this is another option for family research. You don't have to be Mormon to join, and like the other sites, it's free. It also has some cool graphics for your tree, so I'd check it out.
Similar to Ancestry, it's a place to build and keep track of your family tree. I've used it a lot as a cross-reference, as you should never take anything at face value when you do this.