Award Traveler is completely legitimate. I've used them once in the past and so has a co-worker of mine.

As far as I know though, they're only interested currently in US Air miles. I had a check fed exed to me the next day, and literally had a tracking number for it about 10 minutes after I talked to Chris, the owner of the site. He's very fast and efficient and I'd recommend him to anyone if you have miles he's interested in purchasing.