You can try www.reddit.com/r/math although it is not that good. You may be able to digg up something nice at http://planetmath.org/?op=forums http://planetmath.

You can try www.reddit.com/r/math although it is not that good. You may be able to digg up something nice at http://planetmath.org/?op=forums http://planetmath.org/?op=forums . I don't think there is really a nice discussion forum for math :(