The information I had was that we built 5584 on Monday, which was intended to be the release. Another internal source told me a single "show stopper" bug (I'm not saying what - but it mattered to Microsoft internal people more than most users) caused them to go back and do one more build. 5600 was built on Wednesday.
By a strange twist of fate my daughter came into work with me today. I made a DVD or 5600 and installed it on a spare Dell: on which she has been watching DVDs and playing purble palace all afternoon. I'm still on 5536 - yep, the only one in this household to have any time on the real RC-1 is 6 years old ! 5536 -5600 is a a pretty small set of changes, so I don't expect much difference when I put it on this toshiba.
I'd keep an eye on this link http://download.windowsvista.com/preview/rc1/en/download.htm for a location of the download. Technet and MSDN subscribers should be able to download it too. Expect it early next week.
Tagged as Microsoft Windows Vista (Windows Vista)
Update slight fix to the URL, and a newer build is now here.