I have started a wiki page providing basic information related to Qt versions, such as latest major Qt 4.x versions with links to source code, etc.
If you're new into Qt world, Linux-oriented and willing to test some code with older Qt libs, then table with Qt SDKs providing major Qt 4.x versions may be especially useful for you. Why? Qt libs aren't distributed separately in binary form outside of Qt SDK, at least by Nokia.
Forum looks a bit more lively than wiki, that's why I am writing here about it.
Feel free to enhance the content (e.g. by adding links to Qt binaries for previous versions), but please preserve the formatting and conventions used there. Thanks!
EDIT (2015-08-15): Fixed link.
thanks! this is neat :) ...
We are harmonizing the various Qt 5 versions and I will update this wiki with the current Digia related domains.
I finally updated Qt Versions in wiki and all links should be reachable (qt.io subdomains, web.archive.org or ftp.informatik.hu-berlin.de are used). It still covers only 4.x, but I may add 5.x-related sections one day.
I know that usefulness of this page is possibly close to 0 now, as most Qt devs are on 5 now, but I believe we should keep track even of old stuff.