If you're already running the latest build of Firefox's 3.5 beta, you'll be able to upgrade sometime today to a release candidate version Mozilla considers "stable for daily browsing". Direct downloads for everyone, meanwhile, arrive sometime this week.
Mozilla notes that beta testers can get the update a little early by hitting the familiar "Check for Updates" in the Help menu, but an update prompt should also arrive some time today. Anyone else who wants in on a release candidate will have to do the same—download Firefox 3.5 beta 4 from Mozilla's site, then hit "Check for Updates." Thanks Ralph! Firefox 3.5 beta users will receive update to early release candidate [Mozilla Developer News]