Jean-Baptiste Quero, an engineer at Google's Android Open-Source Project, posted on a Google Groups message board, of about open souring Gingerbread source code.
Quero warned that it would take several hours for the code to finish pushing to the servers, but it should all be available now at Kernel.org -- but don't be surprised if speeds are crawling.
And you can bet the dev community is already hard at work doing just that. Custom ROMs (like CyanogenMod) are built using Android source code from the AOSP, so it's now only a matter of time (possibly just days, knowing this community) before new versions of popular ROMs are released with Android 2.3 underpinnings.
Nexus One owners can probably expect an update pushed to their phones sometime soon as well, since it doesn't usually take long after the AOSP release.