I used to crack my wrists constantly back in my younger years, usually in a 360 motion, but I had to stop myself from doing so. I think I used to have pain in my wrists when I used to have that habit. But now I crack my fingers at least once every day or so. I used to crack my back and neck every now and again as well, but now I've developed some serious back issues so I had to stop. =(
And now recently me knees crack when I squat and get up, which I'm forced to do due to my damn back, weird. I don't see myself abstaining from cracking my fingers anytime soon though.