Fresh installers for Evolution 2.22.x for Windows will for now be available at the go-oo.org site, but eventually it will be offered somewhere else.
An olded installer for Evolution 2.8.2 from some years ago is here. (Yes, that page is under a SourceForge project not related to Evolution at all. It's just a project of Mike Pinto, the helpful person who created the installer, and he didn't want to start a new project just for the installer.)
If you want the raw Win32 binaries of Evolution and its dependencies, surf around on ftp.gnome.org. Note, this assumes you know what you are looking for and understand the structure of the GNOME platform software.
And finally, if you want the source code for Evolution on Windows and its dependencies, fetch the official source code releases for them, from ftp.gnome.org (or the GNOME SVN repository). There are no separate "Windows" versions of the source code.
Evolution's official Wiki is at go-evolution.org. It includes instructions how to build Evolution from sources on Windows.
This SourceForge project, evolution-win32, was created with the intent of being "the" place where the porting of Evolution to Windows happens. Alas, that wasn't how it worked out. The porting work, mostly done by Tor Lillqvist at Novell, had all required changes folded into the normal GNOME source code repositories, and binaries were released on ftp.gnome.org.
There has been a sad lack of volunteers helping with the porting work. Volunteer help would be much needed to sort out the remaining issues. Probably an effort will be made to make the Evolution code (and maybe parts of the dependencies, too) easily compilable with Visual Studio. The GNU style build system with configure scripts, makefiles and libtool is probably a large stumbling block for people who might otherwise be interested in helping.
Don't use the SourceForge bug tracking system to report problems with Evolution on Windows. Use the GNOME bug tracker. Be sure to indicate clearly that you are on Windows.
If you want to have a look at this project's original home page, look here. But please note that most of that text was written quite early and doesn't have much to do with reality.