If I didn't wash my drysuit periodically, I wouldn't be able to stand being near myself. Yuck.:11:
I gently wash the suit with a mild detergent, rinse a couple of times, follow with a soak in BC Life and another couple of long rinse sessions. It's important to rinse all the detergent out if you're diving with thermals on - detergent can dramatically reduce the hydrophobic qualities of many kinds of underwear. Hang it inside out until dry (if it doesn't dry in a few hours, put a fan on it), then reverse and let it finish drying before storing. Less stink means more friends and not having to do your surface interval hanging over the downwind side of the boat makes for better diving. Don't forget to take a toothbrush to the zipper teeth periodically to clear out any grit and excess wax.