Another Windows 7 build has leaked. This time it's build 7229. Sources are indicating that unless there is a leak internally from Microsoft, this would be last build leaked before the RTM. The build string is 7229.0.090604-1901 meaning that it was compiled a week ago. Earlier this week, build 7227 leaked to the public.
Initial reports indicate that you can not use your RC keys with this build, so if you want to activate properly you should not upgrade to this build. Update: RC keys are activating fine.
Windows 7 is still on track for a July RTM, and it's possible that it may even RTM by the end of June. Microsoft has announced that it will be available in stores October 22nd.