Sorry, I don't have any personal experience with IBD, but there is a Yahoo Group that is devoted to Feline IBD and it seems like it would be an excellent place to start. From my own experience with the Feline Cancer group, the folks in these groups are very knowledgeable, supportive and civil!
For diet/nutrition, I'd suggest the guidance of a holistic vet because they are much more knowledgeable about food and nutrition than most 'conventional' vets. Unfortunately, many 'conventional' vets don't delve much into nutrition and some are merely "Shills for Hill's". Here's a very good link to help you find a reputable, licensed holistic vet in your area.
http://www.holisticvetlist.com/
And here's a search string for "feline", "diet" and "Inflammatory Bowel Disease":
http://www.google.com/search?hl=en&newwi…