• Experiments with photocells
• Possible photometers to buy

Tutorials from Gamma Scientific:

• Spatial Measurements of CRT Displays
• Color Temperature - A Problem of Standards
• Spectroradiometry

Other URLs Bill found:

• Lecture notes on LCD screens
• Look at graphs relating voltage to intensity [not quite intensity -- percent transmissivity -- it's one link down]
• Really nice review of LCD technology
• High level overview
• Technical specs for a number of LCD displays