The GUIdebook (hooray for icons!)

I happened across this great site called the GUIdebook, charting the progress of the graphical user interface (GUI) design over the years, including Mac OS, NeXTSTEP/OPENSTEP/Rhapsody, Windows, OS/2, and even BeOS, Red Hat Linux, QNX, and Solaris.
My favorite part is the icon camparison chart, but there's also some other great stuff, including tons of old screenshots, a timeline, sounds, and more.
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