Here are a few helpful and / or interesting links:

The 8 bit guy

If you're interested in retro computing or some basics about computers I recommend to watch some of his video clips. Very interesting, very funny, very educational.

GUIdebook - Graphical User Interface gallery

In this gallery you get an overview of how graphical user interfaces have looked like and changed over time. From the Lisa Office System 1.0 on the Apple released in 1983 up to Microsoft Windows Vista released in 2007 you can have a look at many screenshots of these systems.

Unfortunately it seems that this site hasn't got an update since October, 6th, 2006.