It is August 20th here in the US Central Time zone, the last day that you will be able to download the Windows 7 Release Candidate directly from Microsoft. License keys will still be available after today if you have the disc image to install with.
In my previous heads-up on this, I made a mistake in the time table. March is the cutoff date for RC license keys. Here is the updated table:
8/20/09 - Last day that Windows 7 RC will be available for download
10/22/09 - Windows 7 ships (General Availability or "GA")
3/01/10 - Windows 7 RC will begin shutting down every 2 hours; RC license keys no longer available
6/01/10 - Windows 7 RC expires