i agree, your not gonna find a road bike worth it under $400, youll end up selling it for half what you payed for and buying one that cost more...
I purchased a specialized allez triple last fall, $524 closeout price ('06 model) they go for around $700 right now for the '07, and the '08s will be out soon. However, i didnt go into the shop and just hop on the cheapest closeout bike. I looked, knew i wanted a specialized (it was a good idea for me), and got real lucky finding one that fit me, on the clearance rack
i was exstatic to say the least!
Dont buy off e-bay. chances are you have NO idea how to set it up or tune it out of the box, which will end up taking any money you saved and spending it on the local bike shop like you should have in the first place. I have built a bike from parts. But I was young, crazy, and have a good mechanical ability. And, a decent shop will treat you good for years to come, and always have answers to your questions.
by the way, i still have two MTBs i pieced together from parts (one was all new, one was all used). they function probably as good as any bike from the LBS would. but I cant tune a bike as fast as they can. Takes me some time and a few words i dont dare repeat