Better Font Rendering
LifeHacker had a quick little link to techniques to reduce eye strain. The tip that caught my eye was enabling ClearType on Windows XP. It's just subpixel rendering, but I hadn't realized that it made such a difference on CRTs -- I thought it was only good for LCD displays.
Seeing this improvement on my workstation prompted me to just go compare settings on my Linux notebook, and I found that I had actually lost my subpixel rendering settings a while back when I blew away my configurations. I enabled it and was again quite pleased. The settings are accessible in Gnome through the Desktop->Preferences->Font menu option, or by just running
Update (4:50pm): Sub-pixel and even normal antialiasing seem to not work very well for white on black terminals. The white text looks shadowy, but black text on a white terminal looks very nice. I've had to keep a blocky looking "Fixed" font for my terminals, since I use white on black.