www.gtk.org
Home site of GTK+. Check it out if you don't know what this site is all about.
http://ftp.gnome.org/pub/gnome/binaries/win32/
The official GTK+ win32 binaries (zip files), packaged by Tor Lillqvist. This is where the dlls in gtk2-installer come from. You can also download the sources here.
www.gimp.org/~tml/gimp/win32
Tor Lillqvist's Gimp and GTK+ for win32 pages. This used to contain all the binaries until they were moved to http://ftp.gnome.org/pub/gnome/binaries/win32/.
http://www.gtk.org/download-windows.html
The links to files from http://ftp.gnome.org/pub/gnome/binaries/win32/, with descriptions.
www.dropline.net
Dropline systems used to have their own version of gtk2-runtime installer (now discontinued), using the same sourceforge.net project page as we do now. Thanks to Todd Kulesza for allowing me to adopt the project page.
gimp-win.sourceforge.net, Sourceforge Files Area
Jernej Simoncic's GIMP and GTK+ installers (GTK+ may be out of date, because it seems that it has been merged with the GIMP's installer).
www.pidgin.im, Sourceforge Files Area
Pidgin developers distribute their own GTK+ installer which includes some themes and a simplistic theme switcher.