Although some people complained about the stocking section of this website, the compatibility portion for the site was pretty informative. You do have to join but it is free.
You can set up your own virtual tank by selecting fish by scientific name, common name, or by seaching species. I found it great for my tank becuase I was able to find a fairly peaceful chiclid for my community tank.
Good luck
http://www.thinkfish.co.uk/joined.html