What workouts keep you interested?

I have serious workout ADD, I just get so bored after three or four weeks and end up shifting gears completely. Right now I'm in a power yoga, running phase and just before that I was banging out SL. I seem to always fall back onto weightlifting and/or some type of yoga but my mind just can't stay in it.

What workouts do you keep going back to and what do you do to fight the routine blues?