If you are looking for algorithmic puzzles you can browse the archives of topcoder.com : http://www.topcoder.com/tc?module=MatchList http://www.topcoder.com/tc?

If you are looking for algorithmic puzzles you can browse the archives of topcoder.com : http://www.topcoder.com/tc?module=MatchList http://www.topcoder.com/tc?module=MatchList These usually require less time and less math skill than the already mentioned projecteuler.net problems.