As a spin-off of some internal development, our Robot Horde has provided binary builds of Qt 4.8.3 for 32 and 64 bit Linux, MacOSX and Windows (MSVC++ 2008 and 2010) available for free download.

Hope on over to the Qt 4.8.3 downloads page and grab whatever release you need. Be sure to read the Build/Usage notes on the download page.