microwindows.org: Greg Haerr's Nano-X Window System Page (Previously Microwindows)
The Nano-X Window System is an Open Source project aimed at bringing the features of modern graphical windowing environments to smaller devices and platforms.
toastytech.com: Graphical User Interface Gallery
Surprisingly large and thorough Graphical User Interface list, with timeline, screenshots, downloads, links.
Add Site or Add URL to Submit Site to the Graphical User Interfaces Directory