in reply to Project Euler (a series of challenging mathematical/computer programming problems)
Well, I've wasted a lot of time with that site now...
I've solved 18 thus far, and have credited perl for all but #5. A very useful resource for a lot of these is one of merlyn's columns, which calculates the primes pretty quickly. And Math::BigInt is your friend for many of these as well.
Currently, #48 has me a little stumped, as it managed to "inf" out BigInt. All the sums from 18 to 143 have the same last 10 digits, but the site claims that these are not the answer. I suppose I'm going to be forced to think about that one some more. :)