Here is the link to a site that I have found to be a very useful reference tool for approximating the values of your finds. I think it is very well done and easy to navigate. I'm sure a lot of you already use it but for some folks who may not have any other reference, it is a handy site to store in your "Favorites".
Numismedia.com Coin Fair Market Values
Numismedia.com Coin Fair Market Values