I really like Pilates. It feels like a workout yet isn't boring and tedious. I DO enjoy yoga (and I'm only 30 ; ) ), but it doesn't feel like a real WORKOUT to me because it's so relaxing. ALTHOUGH, Jillian Michael's has a Yoga Meltdown DVD that is a KILLER and will work every muscle in your body (even muscles you didn't know you had! LOL!).
If you like DVDs, look up Tracey Mallett. She has quite a few workout DVDs that are a combo of Pilates and Yoga moves. Very simple to follow, and she has them divided up into short segments so you can do 10 minutes here, 10 minutes there, however it best fits into your schedule. She's definitely big on working the core.
I also second the poster who recommended a PT who can help you adjust your gait and your general posture as that makes a HUGE difference in how well you recover as well as preventing more pain. I love this blog written by a biomechanist whose mission in life is to educate people about proper body alignment -- http://www.alignedandwell.com/.....Itemid=223
My back and hips are ALL messed up from years and years of doing exercises the wrong way and doing things like "tucking the pelvis under." Now I'm trying to UNDO the damage that bad posture and gait has done to my spine For that reason, while I LOVED Callanetics as a teenager, I refuse to do it now because she's a big proponent of tucking the tailbone under (tipping the pelvis forward) which is NOT the way humans were intended to sit/stand/walk.
Hope you find just the right workout and can get pain-free!