Been playing Time Fcuk too much lately. It's amazing how many custom levels are being submitted. Seems like a new one every few minutes, many quite good. You could spend all day, every day playing nothing but brand new levels, and I have been.
I submitted a couple of custom levels myself. The first is called Clock Fcuk, control number 1778. I thought it was a clever puzzle when I submitted it at 2am, but it wasn't getting good reviews last I checked. Now I'm thinking it was overcomplicated. Also, I made a mistake in the second quadrant -- you're supposed to place two blocks on the correct key "+" squares, but you can advance after only placing one.
My second level is DgiDgu, control number 2298. It was faring better in the ratings before it scrolled off the bottom of the "Recent" list. It had fours in both Awesomeness and Difficulty. It's sort of a tribute to Dig Dug. "Just needs some inflatable monsters..." You dig your way through the levels using blocks to break walls.