If you are a programmer, then it is highly likely that you are aware of Stack Overflow. You might even be aware that Stack Overflow has a bunch of sister sites, which can be found at Stack Exchange.

One of these, math.stackexchange.com which I found particularly interesting has just gone out of beta.

Like Stack Overflow, this site is a Q and A site, but instead of focusing on programming, it focuses on mathematical questions.

No doubt that this site will be a lot of help to programmers as well as mathematicians.