Crafts can get expensive and if you don't have people that would like to have your craft, you will either end up with a house full of your craftiness or tossing it.
I took up painting. I enjoyed it and did it for awhile. Wan't sure what to do with all the painted canvases lying around the house so when we moved I tossed them. Well, all but 2 because my parents wanted one and one of my friends loved the abstract butterfly thingy I painted. There was one painting that I did that I did want to keep, but it diappeared...anyway, way off topic there.
I used to cross-stitch. I enjoyed it and it was very relaxing and easy to do while watching TV. I also did this with my step-daughter when she was younger, but she didn't like it so much. Knitting I really wanted to do. But I find it very difficult. I've been trying to make my scarf for 2 years now...I don't even have one line yet.
But really, find something that you enjoy. As Mal said, walk through Michaels or Craft 2000 or JoAnne fabric and see what strikes you as interesting. And if you decide to make potholders..you can send those my way...mine are getting old and I don't feel like making new ones just yet.