If you have a scanner and photoshop, here is a great tutorial.
http://pshero.com/archives/turn-your-signature-into-a-photoshop-custom-shape
I found using a tablet really cumbersome to make a signature, perhaps because i'm left handed. Plus you can't tell if you're going to be straight or not.
If you do want to get a tablet, the wacom bamboo is decent and fairly cheap at around $79.
If you want something higher than that you would have to go to the intuos, which I think is around $250 to start.