One program you should definitely look into for graduate work in
scientific illustration is the Science Communication program (specifically
the illustration portion) at the University of Santa Cruz. I believe
Rhode Island School of Design has graduate courses in the subject,
though it's been a while since I've read about it. There is a pamphlet
put out by the Guild that covers courses and programs in scientific
illustration that could give you alot more details. I think you can
find an order form on a past newsletter issue. Hope this helps.