Where can I buy a wide range of used bike parts online? Does anyone know of a reputable website that sells a wide range of used and second hand bike parts and components? 

I'm helping a friend rebuild an older commuter bike and we are having trouble finding compatible components. There are a couple of local shops that carry used parts, but not having any luck there so far. I know of an Ebay seller that sells used ski equipment; I'm wondering if, likewise, there is a website for used bike parts. I'm basically looking for a larger inventory than my local area.
Loose Screws Small Bicycle Parts has a decent selection of small parts.