The only Atlanta aquarist I know of (other than a couple of people through books) is David Ramsey, a great guy who is into killies and N.A. native fishes. He isn't into guppies, though I'd bet he has had them and breeds Corys, but he is bright and gracious and has a nice web site. ;)
http://www.djramsey.com/tropfish/

There are several pretty useful lists of Aquarium Societies on-line. Let me mention for your benefit and the benefit of others:
http://ourworld.compuserve.com/homepages/greatercity/links1.htm
http://www.ifocas.fsworld.co.uk/

There is, as I actually knew, an Atlanta Aquarium Society. Their site, down at the moment, is

http://www.atlantaaquarium.com/

Their contact person is:
Atlanta Area Aquarium Association
    George Libby
    1730 Rhett Butler Drive
    Lilburn, Georgia 30247
    (404) 978-2117

But wait! There is also a local guppy group, which I was unaware of! I hope Snellville is sort of close. ;)  (Having traveled 120 miles each way Saturday to and from an auction and 50 miles each way Friday night to get to my killifish club, I can appreciate traveling to fishy events. I know people on the great plains and even upstate New York who drive 6 hours each way to meetings or just for visits with other fish heads.)

Georgia Guppy Group
    2346 Hidden Lane, Snellville, GA 30078, Alan E. Opdyke, Phone: 770-484-3250, Fax : 770-484-3301. Meets the 3rd Saturday of every month at 1 PM.

There is also an IFGA associate, though the Deep South to me is probably like the Midwest to a lot of others and a huge area. So while they are not close to you, the IFGA end of the year celebration is a whole lot closer to you, than it is to me. ;)

Deep South Fancy Guppy Associates (IFGA) Sponsoring the IFGA  annual meeting (There national show at the end of the year.
Show Dates November 4th, 5th & 6th

http://groups.yahoo.com/group/DSFGAgroup/

2562 Commanche Drive

Birmingham, AL. 35244

Norman Richardson 251-479-4838

nguppyman@aol.com

You mention growing up in Iowa. (I've been in Illinois most of my life, but have yet to grow up.) There are a couple of legendary aquarists and clubs from Iowa. Joanne Norton seems to have had more to do with organizing the ALA (American Livebearer Association) than anyone else. She was also very involved in developing and researching and publishing articles on many livebearer strains. I believe she was involved with the Central Iowa Aquarium Society. While it is no longer with us (too many aquarium societies have come and gone), they did some terrific things. One enduring contribution to the hobby (if my informant is correct) is they realized that the beautiful butterfly Goodied (endangered even then in Mexico and almost extinct in the wild now) had a very tenuous hold in the American hobby. They got several members to crank them out and send them around the country. It has been suggested that virtually all of the Ameca splendens in the U.S. hobby came from that stock.

Gene Lucas is a professor who is very involved in Betta genetics and who has written a column on Bettas with FAMA magazine for approaching 30 years.

I am acquainted with a couple of very talented and innovative guys out of the Cedar Rapids area. I owe them a lot for some of their insights and approaches to the hobby. There are still a couple of good aquarium societies in the Hawkeye State as well.

As a kid, lived six blocks from a big aquarium society and walked by the savings and loan building it met in, while walking to school. Nobody took out the Innes book or Axelrod and Vorderwinkler's Encyclopedia out of the junior high or high school libraries as often as this fish geek did. The month I left for college, someone mentioned that club to me! It was gone when I had time to look for it later. Isn't that the way!