I joined a gym and have been going 4 times a week min. I mostly use the bike, stairs and elliptical at the gym and want to alternate home work outs with gym work outs. I am looking for some core work outs I can do at home, but I don't really have the money to spend on expensive dvds like insanity or p90x... does anyone know where I can find some good moves to do at home for cheap or free?