Using the piston mod and redstone repeaters, I made a timed piston lava course.
You just press the lever on the right, and then you try to jump across each one
without falling into the lava.
The stepping stones will sink behind you so you have to be quick about it.
The timed maze is driven by redstone repeaters below the lava.
Here's how the structure looks disassembled without any lava.
The redstone repeaters introduce delay into the circuit to ensure
that you have enough time to jump from block to block.
I think that pistons are just a really awesome idea,
and I hope that Notch adds them in the next release.