Regular expression crossword puzzles!

I'm on record as being a big supporter of learning regular expressions (AKA "regexp") -- handy ways to search through text with very complex criteria. It's notoriously opaque to beginners, but it's such a massively effective automation tool and drudgery reliever! Regex Crosswords help you hone your regexp skills with fiendishly clever regular expressions that ascend a smooth complexity gradient from beginner to expert. (via Kottke)