Is there a physics Puzzles site like Project Euler?

I think the Harvard physics problems of the week are pretty nice:

Link

One nice source of physics problems is books which catalog questions from graduate school qualifying exams. For example:

• University of Chicago Graduate Problems in Physics with Solutions
• Princeton Problems in Physics with Solutions

Another source of tricky problems is:

• Boston Area Undergraduate Physics Competition.

The contest is sadly extinct, but problems (and solutions!) from the contests that took place 1995 - 2004 are available online.

Just like the example student offered, this one isn't active any more, but makes a nice compilation:

Link