I think weight exercises are way too overrated and misunderstood. People think they can take a single exercise, load themselves up with a lot of weight and that is enough when in fact this is just asking for problems. Weight exercises require a lot of knowledge, you need to know which muscles you are training because you also need to know how to train the other muscle to keep things in balance and you also need to know how to watch for trouble.

I would personally recommend almost anything else -- running, swimming, natural weight exercises (ie. when you are in unstable position lifting your own weight), that train a lot of different muscle at the same time and help keep things in balance.