Prenatal workouts

I worked out regularly before getting pregnant. When first trimester hit hard, I stopped being as active (bad, I know). I went hiking and made a point to move around, but I stopped running due to my big boobs becoming even bigger boobs that hurt like hell bouncing up and down, plus I was exhausted, nauseated and out of breath. I continued to dance (jazz), but eventually stopped because it was too late and I couldn't stay awake enough for it. (I sound like a real thrill, huh?) Now I'm 25 weeks and know that I need to do SOMETHING to keep my body going. What do you all do? Running is definitely out, but I do own a treadmill and can start walking on an incline, if nothing else. Any favorite workout DVDs or routines?