Seed Savers Exchange: www.seedsavers.org
A network of home gardeners who grow and maintain heirloom vegetable varieties. Annual membership allows you access the the network, so you can offer and request seeds.

Nolin River Nut Nursery: www.nolinnursery.com
An excellent source for many varieties of grafted nut trees, and a few fruit varieties.

Just Fruits and Exotics: http://www.justfruitsandexotics.com/FruitHome.htm
Located in Crawfordville. Good selection of perennial edible plants, including olive varieties that reportedly do well in North Florida.

Edible Landscaping nursery: www.eat-it.com
Good catalog, good selection of food-producing plants. Prices are not cheap, but for some varieties they seem to be the only supplier.

ECHO: www.echonet.org
Located on North Fort Myers, Florida. Devoted to fighting world hunger by helping people feed themselves. Promoting sustainable agriculture that relies on a minimum of technological or economic resources. ECHO supplies seeds, plants, and information. Many seeds are available for mail-order from their website, including the amazing moringa tree.

Peters Seed and Research: www.pioneer-net.com/psr
Vegetable and grain seeds. Located in the Pacific Northwest, which might not recommend varieties adapted to that climate for our conditions. BUT – they actually offer a few selections of perennial grains, probably the only commercial source to do so. The perennial sorghum varieties probably have a good chance of doing well in Florida.

Miscellaneous :
Here are some links to edible nurseries!
http://www.tropicalfruitnursery.com/
http://www.naturehills.com/

Lots of great links here also including a forum discussing edible nurseries:
http://forums.gardenweb.com/forums/load/edible/msg0907152314910.html
http://www.simplelivinginstitute.org/links.html