Algorithm/Programming Contests and Resources
The most popular algorithm contest (also closely watched by the industry) is Topcoder: http://www.topcoder.com/tc
The ACM ICPC is an IBM-sponsored on-site contest with worldwide recognition and participation: http://icpc.baylor.edu/icpc/
The ACM ICPC problem sets are available online here (some of the problems are really very challenging): http://www.acm.inf.ethz.ch/ProblemSetArchive.html
The ACM Valladollid Online Judge System lets people solve problems at their convenience (no time limits) and get them judged for correctness, and get world and country specific ranks: http://icpcres.ecs.baylor.edu/onlinejudge/
The Sphere Online Judge system is also another popular programming problem source similar to the Valladolid Online Judge System: http://www.spoj.pl/
Google Code Jam is a coding competition sponsored by Google, hosted by the Topcoder platform. It is expected to happen again in 2008, possible hosted independently.
Bitwise is an algorithm-intensive programming contest hosted every year by IIT Kharagpur, with fairly stiff competition: http://www.bitwise.iitkgp.ernet.in/