I like to use the elliptical machines to mix it up with running. It's easier on the knees and I can really get a sweat going on it.

Also swimming is fantastic..helps build/strengthen core muscles and shoulders, helps with lung capacity, great for joints and flexibility. I would swim more but I smoke too much weed. That is not a good conditioning program, yet is still one I find very effective

I also like to get on the stationary bike, hold a 10 or 15 lb weight in each hand and do rolls and obliques with my upper body while peddling on the bike..another thing that gets me sweating a lot and you work abs and shoulders while doing cardio