A great list was put up at inter-sections.net on how to recognise a good programmer. Check it out, it is definitely a good read.
One of the comments (by Ashley Moran) struck me as very true also, “Also, something that has stuck with me long after I forgot where I read it (possibly the Jargon File?) is that you should look out for developers with highly-developed outside interests. Generally, the ones who excel at or show extreme dedication to their hobbies are better hackers than those that don’t.”
I would agree 100% (maybe because I have highly developed hobbies?) that people who develop their outside hobbies give them much more perspective in which to reference and resource the work they do in development each day.