Based on what I've seen first-hand, along with what third-party sources have been telling me, Windows 7 RTM build is build 7600.
I've had a look at this build today (I don't have a personal copy yet but will do so by the end of the day) and there doesn't seem to be many, if any, changes between this build and the Release Candidate build.
I'd expect an official announcement real soon, along with the build appearing on MSDN, TechNet and Volume Licensing customers.
[UPDATE: Or maybe not ... what is clear from the latest leaked builds is that the RTM build will be virtually indistinguishable from the RC release. In fact, Brandon LeBlanc might have actually offered up the reason why Windows 7 isn't yet RTM -ready:
"Windows 7 will be available in many languages from around the world. For us to consider RTM “done”, it requires that all languages be completely finished. So there is a lot of work that needs to take place for us to finalize all languages of Windows 7."
I'm pretty sure that under the new regime at Microsoft's Windows group that if Vista was being released now, that all those Ultimate Extras we were told about would have to be finished before RTM. Maybe patience is a virtue!]