Originally Posted by Expatriate
Qbike.com searches several sites, plus ebay. In my experience pricing several thousand dollars worth of parts each year, I can honestly say no one site covers them all, but qbike should be your starting point. It give you a quick point of reference for the others. I've noticed many regular ebay sellers will still come in below the major sites.
Don't know about E-Bay but there are so many on line shops out there you are spoilt for choice, just look at as many as you can.Problem is, you wont build a bike from bits cheaper than you can buy a complete bike.
I built up a custom hand made frame a few years ago, but had the sense to have kept all the old bits when I upgraded my old bike. Basically I had a donor bike with all the right bits on for the new frame. I then replaced all the old parts on to the donor frame so then had two bikes. Problem was, for the next 6 months or so I still prefered the old bike with the crappy parts on it.