Running definitely helps - would running on a treadmill be any easier for you? I think the ellipitical helps too, but I think running is way better. And as others said - definitely squats!
I don't have access to a gym so machines are out. I've been trying to motivate myself to run for awhile now. Maybe if I know it will help my tush, I'll start. I'll start the squats ASAP.
I'm having really good luck with the treadmill - I put the grade on 15, or as high as it will go, and walk steadily, 2.5 to 3.5 pace, for a half-hour. I alternate with teh ellipitcal every other day, too. The ellipitcal helps my but, but the treadmill gets the back of my thighs better.
I;m an avid runner but days I don't feel like running I do intervals. Say run for a minute, walk fast for 4 minutes etc for 30 minutes, 20 minutes whatever. Any running is better than no running. Walking on an incline helps also.
I'm in a kickboxing class right now, and I've started running...and I notice a slight difference, but my kickboxing teacher also teaches step aerobics, and she says within a couple of weeks of starting that program again she always notices her butt is a little higher...