Where to Buy Stuff

Buying Slugs
Carolina Biological: Carries E. clarki.  Not currently selling to indiviuduals.
LiveAquaria: Hesitant to tell you which species they will come up with, but it will probably be E. clarki
KP Aquatics (formerly SeaLife inc): Carries both E. clarki and E.crispata. Very responsive to special requests.

Food Plants:
Gulf Coast Ecosystems: Carries a wide array of Caribbean and Gulf macroalgae.
KP Aquatics (formerly SeaLife inc): Avrainvillea, Halimeda, Penicillus, Udotea

Equipment & Supplies:
Florida Aqua Farms: Supplies for aquaculture, including nutrient mixes for algae
Premium Aquatics: Large selection of supplies and equipment for marine aquaria