I do pelvic rocks and chase my kids around. I plan to walk when the weather is nicer, but it is too cold for the kids right now (although today was nice so we did take a walk).
I keep meaning to do my prenatal yoga DVD, but somehow that just doesn't seem to get very high up on the priority list
I never got around to prenatal yoga with DS2 either, hee hee. But I did go swimming for a few months this summer, and rode my bike a lot, and walked everywhere (we don't have a car and live in a city).
Pretty much any and all physical activity is good idea, I don't think it really matters what it is!
DS2 - Oct 2010 (my VBAC baby!)