I love to do Leslie Sansone's You Can Do Pilates, so I usually do that at least every other day. Since it's only about 15 minutes long I also do one of the DVD's that McDonald's was giving out a while back if you bought a salad. I have the cardio one and the strength one. They are each 15 minutes also, so I add one of them with the pilates.
I've also given yoga a shot for the first time this week...I did enjoy it, it was very relaxing.
I also like to get different videos/dvds from the library to try out different things. I figure if I don't like it, no harm done since it didn't cost me anything!