What is a reliable, authoritative source to find out what the latest stable release of Ubuntu is (if there is one)? Ideally this should exist somewhere fixed on the web, and should always tell you what the current latest stable version of Ubuntu is.
At the moment http://www.ubuntu.com/desktop mentions 14.04 and doesn't mention 14.10, so one might think it's 14.04. http://www.ubuntu.com/download/desktop/ calls 14.04.1 the "latest version" (the distinction between 14.04 and 14.04.1 is not my point here). But http://releases.ubuntu.com/14.10/ doesn't mention "beta" or "RC" anywhere, which leads one to think it's the final release. But it's not clear if one is "supposed" to look at that page directly. https://wiki.ubuntu.com/UtopicUnicorn/ReleaseNotes sounds like it's 14.10, but then it's a wiki page...
(Note: the question is really what is stated in the first sentence, not "what's the latest stable release right now?")
The site https://wiki.ubuntu.com/Releases pretty clearly indicates that 14.10 is a future release, which should indicate to you that this is not yet a stable version. 14.04 is listed as a current release, supported until April 2019 which should indicate to you that Canonical considers this to be a stable release.
http://www.ubuntu.com/download/desktop
That's my answer to this somewhat silly question. If there's a stable release it will be put on the downloads page when it's ready.