I saw a post on bimmerforums that showed someone connecting the unused sockets in the rear tail lights and decided I would get a little more detailed with it...
Items Needed Drill w/a 3/32" and a regular phillips head bit
4 small sheet metal screws
4 3/16" washers (can be either split or flat)
wire
circle terminal ends
wire crimpers/strippers
Time from start to finish: about 20-30 minutes.
1. Take off the tail light circuit by turning the knob attached to it and unplug it from the harness on the bottom.
2. Using the drill (of course) the appropriate holes in the metal (shown by orange circles).
3. Cut the wire into 2, 4"-5" pieces and strip off the ends of it. Connect the wire terminals to the end.
4. Using the screws and washers, connect the wire to the holes you made earlier. (shown by orange circles)
5. Replace bulbs and reinstall the circuits.
6. Pop open a brew, push on the brakes, and admire your handywork.