Well to start off, you can look through Ido's work on the stall bars including front and rear supports, one arm HLL.
What we did on the stall bars during the seminar was a lot of the HLL and then stretching. We also used it for Flag/Side lever.
A fun drill was to hold the bars as if for Flag and walk up the ladder with your feet. Yes, my boys loved that.
They are also very useful for floor glute ham. I figured out a way with a swiss ball to duplicate a GHD device.
Besides HLL, you can also do inverted leg lifts but bare in mind these are pretty easy in general.