I keep a copy of my FSM on there too, as well as any manuals I can get in PDF form. I also have some reference images but most of them are more scientific than practical, like the tap/die charts like menitoned above.
A friend of mine who runs a printing press in his garage keeps test patterns/color references available so he can pull it up on the screen. Guys who do painting could probably get away with something similar, but you have to get very expensive (PVA or IPS if you get a panel, I have a CRT still) monitors specifically for their color-correct features. If you use any old screen you won't necessarily be that close to what the pigment will be, and of course you might not want to keep an expensive monitor like that in the garage.
