Check the Roku site - many retailers are now carrying them. I recently (this week) got mine at Best Buy.
Being the geek I am, I've got and Xbox 360...but its not in my living room, and I've also got a laptop, but using it for netflix streaming onto my HDTV is awkward and just isn't a very streamlined process (sitting on a stool right in front of the HDTV clickity clickity.
Decided maybe a $99 Roku isn't such a bad idea, but then I look and find its online order only. Why is it all the best stuff can't be bought at a retail store...or maybe I should ask, why the heck do we still have retail stores. None of the 'good stuff' is ever there, so the impulse buy just isn't happening.