Bikes Direct. They're the same entry level bikes offered by other labels for a couple hundred bucks off.

Building up a bike from a frame is fun, but it adds up pretty quick. I bought an old Schwinn steel frame for $20 at the local bike collective, did the math, bought the Messenger on BD, and it's been an OUTSTANDING bike (for what it is, a solid basic chromoly steel fixie). Then, since I like to tinker, I went back and started buying parts for the Schwinn. (The $20 frame is turning into a $500ish build, because when you want something that reflects your taste (or lack thereof), you tend to get picky.)

Also, the Langster is aluminum, and has a more compact style rame, while most of the BD bikes are traditional geometry steel frames, which tend to be preferred by a lot of the Tarck crowd.

Buy the bike that you can afford that will make you happy.