I love yoga and highly recommend it, especially for breathwork, calming, and inner focus. I'd recommend a class, too, particularly a beginner class and/or one for people with any physical limitations. If you find the right teacher, you'll probably be able to learn from her/him if there are any specific poses that are best for you.
At the very least, Pranayama (the yogic art of breathing) work is empowering and may be able to help you through difficult and painful times with UC.
There are lots of different schools of yoga that range from really fast moving, physically demanding to very slow and also physcially demanding to very relaxing and meditative. The main thing to remember is yoga is not a competitive sport.
Potato... Female, 58, dx mild left sided ulcerative colitis 11/07
asacol 3 3x a day
cortenema am & pm
culturelle, benefiber wafers
children's vitamin, Vitamin E 400 mg
omeprazole 2x a day
oxazepam (anti anxiety) when needed, lomotil if needed (trying this out)