I was diagnosed last year. Fortunately I see a Parkinson's nurse every 6 months. She is really good and reassuring, as well as tweaking my meds so that I slept better after a few months on the new regime.
She also said how important it was to keep moving. Parkinson's uk has a brilliant DVD and booklet called just that - "Keep moving". When I first watched the DVD I couldn't see how their recommended exercises would help, they're so gentle. But they really do, as they they are designed specifically for PD people.
I've also started Tai Chi classes. No special clothes, no mat, no rubber bands needed.That works for me too. I actually joined U3a so that I could join their reasonably priced classed that were clearly targeted for the members (ie those of us of more mature years!)
It's really worth trying a few activities till you find one that you like and that suits you as not only does it help with stiffness but I always feel better in myself for having done a bit of exercise.