Any one know some good math forums? For exampmle, to discuss stuff related to Discrete Maths, Linear Algebra, Number Theory, Algorithms & Complexity and etc. I'm aware of usenet groups but if you know of any good forums please let me know. Thank you.
The definitive site for discussing math is
artofproblemsolving.com
for discussion of contest-style problems.
Some of the other online forums are restricted to persons in particular professional associations; Art of Problem Solving is open to anyone, and well moderated.
How do you see yourself interacting, and what are you trying to accomplish?
On the other hand, the overall skill level at AoPS is very high and very contest math oriented. I don't really check it that often anymore but in the past it never struck me as discussion forum as much as a problem solving forum (or a "how to become a better problem solver" forum). In addition, the majority of the posters there are young, that is high school age and below (though there are still a fair number of older posters).
To put it a different way, when friends of mine that are interested in learning "interesting math" from a casual standpoint ask me where to look, I'm not really sure what to tell them. Certainly I recommend giving AoPS a shot, but I'm unsure as to whether it would be the best place to go.
xkcd - http://forums.xkcd.com/
#math on freenode
1) MathForum.org
You can check out the previous answers here:
2) Yahoo! Answers (Home->Science & Mathematics->Mathematics)
On Usenet, you're probably already checking math.sci. That's my favorite one.
-Larry
The definitive site for discussing math is
artofproblemsolving.com
for discussion of contest-style problems.
I don't think there is really a nice discussion forum for math :(