Saturdays: I do cardio and abs. Since I don't work weekends, but end up waking up at the ungodly early hour of 530 or 6 AM anyway, I usually end up going jogging in Coconut Grove (nice area by the bay, here in South Florida). It's a nice way to start the weekend.
Sundays: supposedly my "rest" day, but sometimes I'll go jogging or rollerblading (it's been a while for that though), and once in a loooong while, I'll go to the rock climbing gym. For the most part, I take sunday to catch up with my parents, cook most of my meals for the coming week, do laundry and vegge out for a while.