Mathlinks aka Art of Problem Solving

This is posted by LJ's mum.

Mathlinks is a website/forum that Lim Jeck frequents, on an almost daily basis. It is where he hones his Maths Olympiad problem solving skills. Since joining Mathlinks on 10 March 2010, he has contributed 760 posts (as at 25 January 2011) which works out to an average of 2.73 posts per day. Out of a total of 78,927 members, Lim Jeck aka oneplusone is currently ranked the 455th most active user. The most active user has to-date made 12,301 posts in the various forums!

He also participates in an unofficial Olympiad Marathon initiated by a fellow forum user. Currently, he is ranked 1st, after some 14 rounds of questions.

Art of Problem Solving

I think The Art of Problem Solving is the best resource for Maths problem solving. You can also train your quick thinking by playing Maths games with other people. Try FTW! to pit your Maths skills in solving AMC kind of questions against other Maths enthusiasts. At the end of a game, you will be rated against other registered players.

If you have any Maths problems, go to mathlinks.ro and post your problems there (instead of spamming my cbox :) ), and hopefully someone else will answer it for you. It has forums for primary school kind of Maths questions, to high school types, to Maths Olympiad questions, college/university Maths and even Arts and Sciences.
http://www.artofproblemsolving.com/Forum/index.php