I've used plenty of free wordpress themes in the past for my sites. There are a ton of them out there that are very nice looking. Just pick one and get started.

Last year I bought the Thesis theme package and really liked it. But it does have a very steep learning curve. The good news is they have a helpful support forum you can go to to work out the kinks.

I recently got the ProPlus Theme Package from StudioPress. It is absolutely amazing. Great templates to work from. I recently implemented one of their themes on my denisoberry.com site. It was quick and easy. They also have an awesome support forum. You can get an answer to any question you have.

Just a word of caution on free themes. There are some bad people out there who will stuff the theme with hidden key words. So make sure you are not getting a theme that has something like that in it.