Good Source For Stamp Values On Internet

I am about to sell the many international stamps from my father's collection. He was active in the late 30s and then picked up the hobby in the late 40s. There are quite a few that I would like to sell on ebay, but would like to find a good source that talks about values, etc. I know I can look at previous sales on ebay, but are there other places I can check. I am more familiar with coins, where there is V-coins. Is there something similar for stamps?

Many thanks.

Best thing to check is local library for a recent set of Scott catalogs. But using ebay and Bidstart you should get a idea of values.