If you have a motherboard you go to the maker's site and look at the CPU list for that board.
Are you trying to avoid this work?
I'd like to build a pc from old parts for a friend and would like to know if there is a quick way to tell if all the parts are compatible with one another. For example, would motherboard X be compatible with cpu Y, and would cpu Y be compatible with fan Z, etc. I plan to purchase half or more of the parts online, perhaps on ebay and/or amazon.