Water clock[]
Water Clock
Up and down[]
A Loadbox[]
Redstone Roses
Compact JK Latches[]
Courtesy of Munin295:
The J and K inputs need to be at least 2 ticks long. The circuit delay is 2 ticks, but it takes time to stabilize for the next input so it can only handle a 5-clock (e.g., a 2 Hz clock line).
You could make it a flip-flop by feeding a falling-edge clock line into the other sides of the input comparators. Also, I think if you build this facing east or west, you can move the piston back one block and adjust the rest to make the circuit one block shorter (it needs the repeater for the general design because of the circuit breaker directional bug).
Munin's hopper JK
Another Munin JK
Discussion at http://www.minecraftforum.net/topic/1799092-so-anyone-have-a-compact-jk-flipflop-yet/#entry22311242