If you're looking for a challenge to keep you occupied for a while and want to flex those developer skills, check out the Toughesst Developer Puzzle Ever as created by Jeff Blankenburg.
For the second year in a row, my friend and colleague Jeff Blankenburg has created what is quickly proving to live up to it's namesake - the Toughest Developer Puzzle Ever. Some of the puzzles are technical, some are not but all require that you understand the web, development and technology to solve. Even if you don't get in on the fantastic prizes that Jeff has lined up, there's great bragging rights in being able to solve the Toughest Developer Puzzle Ever.
Josh Holmes (whose blog is linked above) was the creator of three of the levels of this difficult puzzle. Give it a try if you're looking for something to really stretch your knowledge!