MathLinks: This is a site of web based fora, very active community of young (mostly, very young) mathematicians, originally introduced as a Math Competitions Site, but currently, even when this is still the main topic, you can find a huge variety of topics there. This great site was originally designed by Valentin Vornicu, who is still one of the administrators (probably the most active of all, but I am not sure)

Snark: This is the site of the e-mailing group Snark, a group created for the discussion of puzzles and other interesting problems that can use two or three of your neurons for a while. Its language is Spanish, and there is no way around, because even when its members use to speak other languages, spanish is the only common to everyone.

PQRST Puzzle Competition: PQRST is a quarterly and online puzzle competition open to everybody. Competition will be in January, April, July and October, created by Cihan Altay. You should try the next edition, Cihan really does a great job.

Purdue's Math Problem of the Week: This project is way older than the one I organize, and is somehow the one that inspired me to do it. You should also give it a try.

Kalva homepage: Math Problems: This is a site with the recopilation of a lot of Math Competitions around the globe. It was created and is maintened by John Scholes. It is by far the best recopilation of Math Competition Statements that I have ever found on the web.

Wikipedia, The Free Encyclopedia: As its name says, it is a free encyclopedia on the web. It has almost half a million articles in English, around two hundred thousand in German, almost fifty thousand in Spanish, and well, a lot more in other languages. You can also create and edit your articles

MathWorld: This is a site of mathematics. One of the better organize and more complete specialized encyclopedias ever, and it is free online.

GT Hapkido: This is the site of the Hapkido Club of Georgia Tech, and in my opinion, the best martial art club that you are going to find. It is associated with the Black Knight Dojo. If you are interested on martial arts, and you are at Georgia Tech, well, give it a try!

School of Math, Georgia Institute of Technology: This is, of course, the website of the school of math here at Tech.