There are a lot of posts on this forum asking for ids on mystery sunfish. Here's an online sunfish (including "basses" in the family Centrachidae) key from Richard Mayden at the U of St Louis. It works best with the fish on a pan in front of you, but in this key Mayden uses a lot of uninvasive traits that you can get off a live fish (or a clear photo). Just thought I'd throw this out there.
http://bio.slu.edu/mayden/sunfish/sun_key/1.html
http://bio.slu.edu/mayden/sunfish/sun_key/1.html
