A friend and I made some puzzles -- it's still being made, so it's not perfect, but I have showed it to some friends so far and they're addicted and asking for more puzzles.
If you'd like to check it out here's the link
Cyanide-x
There is a link there to join us on irc -- this could be a huge help if you get really stuck.
The puzzles' difficultly varries. I think as we add more and more puzzles we'll have to reorder them a bit... level 16 and 17 are our toughest puzzles, I'd say.
Feel free to tell us what you think of it.