any sites for good problems in mathematics?

Answer 1

It would depend on what type of problem for which you're looking. Something recreational? A tutorial? What level?

Here's a mess of math sites, but for problems, I could give you a better answer with more details.

http://mathworld.wolfram.com/
http://www.purplemath.com
http://www.math.com/
http://www.aaamath.com/
http://mathforum.org/dr.math/
http://mathforum.org/
http://www.aplusmath.com/
http://www.coolmath.com/
http://www.emis.de/ZMATH/
http://www.mathgoodies.com/
http://www.k111.k12.il.us/king/math.htm
http://www.math2.org/
http://www.webmath.com/
http://archives.math.utk.edu/
http://www.sosmath.com/
http://www.mathplayground.com/
http://www.w3.org/Math/
http://www.pbs.org/teachersource/math.htm
http://www.funbrain.com/math/
http://www.mathstories.com/
http://www.khake.com/page47

Answer 2

Mathworld or Mathworks

Answer 3

www.maths-maths.com