I'll pimp the Rush Hour a little. Under $600, a trackish frame with no braze-ons other than the rear brake bridge that comes with everything you need to set it up as a singlespeed or fixed gear (or flip-flop). I put well over 1000 miles on it in 6 months, and it held up fine, with only the wheels going out of true by a couple of millimeters. It can be converted to a traditional fixie and gives a very clean look without decals or braze-ons (and you might be able to Ebay the leftovers for a few bucks). The biggest issue is that the paint chips very easily.