According to Wikipedia
: Windows 7 RTM is build 7600.16385
I assume the number after the period is the one changed with various hotfixes, and the "major" number (7600) may be changed with service packs.
That's the final RTM build.
As i understand it, 7100 was the final RC build and 7105 was the first post-RC (RTM) build.
Perhaps, I've seen b7165 or so as well, but I'm not much interested in various leaks, only the official releases concern me (of course, I don't have access to any official MSDN-only builds that may or may not have come in between the RC and final RTM either, so it's really only the open betas, rc's and finals I care about).
If you're in one of the groups that got the privilege of access to a more closed test version, fine, good for you. If you're in the group that found a leaked copy of said version on some torrent site, fine, good for you. But for the non-pirate and non-privileged enthusiast, there's nothing between 7100 and 7600.
Bah, what the heck, I am a pirate, but I just don't find it worth reinstalling the OS that often, I got the betas to try out in a VM but didn't bother running 7 as a main OS until the RC was released, and never bothered to try the in-betweens as they weren't meant for wide-spread testing anyway (and a VM isn't a very good testing system).