I use the Leslie Sansone Walk Aeorobics ones and love them. During each session she has someone at walking pace and someone as a brisker/jog pace so you can choose what you feel up to. I've also got her kickboxing one. She has great variety and I love that she loves to laugh at herself!

I also have a Windsor Palates one that I love.

You can sometimes get them a little cheaper of ebay.