NANFA has a newsletter. Also there was a good article in TFH a few years ago. Some of the old fishkeeping books from the 50's had some info as well. There's a couple of good books, try looking on amazon.com
Olive
I would look on amazon as was already stated, also if you do internet searches for specific species you can sometimes find care guides, I found a nice one for perch a while back, though they are generally based towards aquaculture they have a lot of good info in them. Again the NANFA also has a magazine or used to I think it was called currents or something.