If you leave your PC idling frequently, you can contribute your processing power toward discovering Mersenne prime numbers. Besides the awesomeness of being part of a worldwide supercomputer, as well as an esoteric and enigmatic endeavour, you can win $3000 up to $50000. In all honesty though, the fact that a Mersenne prime could be named after you, is a better reason to join.
"If teaching is reduced to mere data transmission, if there is no sharing of excitement and wonder, if teachers themselves are passive recipients of information and not creators of new ideas, what hope is there for their students?" —Paul Lockhart