How long does Apple provide support for Mac OS X? I am currently using Apple 10.6 (Snow Leopard). How long will Snow Leopard be supported for? Does Apple provide an end-of-life policy in writing?

I have read that Apple tends to only provide security updates for the latest two versions of Mac OS X (an 'n-2' support policy, where 'n' is the latest version of the OS. Since Lion and Mountain Lion are out, Apple might drop security updates Snow Leopard.

According to "Mac users left wondering if OS X Snow Leopard's retired" from Computerworld and "Where are the Safari security updates for Windows and Snow Leopard? Users left exposed" on Sophos's blog, some believe that Apple has already, quietly retired Snow Leopard. However, those pages have some contradictory information (Tiger was updated in 2009).

However, the articles above seem to cite rumor. Does Apple provide their support policy in writing?
Apple don't provide any end of life information unfortunately, and you're correct that they only support the current and previous versions, although they do still release security patches for the one before that from time to time for another release cycle after this.

So you'll get up to 3 years out of an OS release, and that usually an Apple computer will be supported by new OS releases for around the same time.