Even though it's clearly biased** towards the new Park Spoke Tension Meter, Cyclingnews' article "Balancing wheel tension with the TM-1 Spoke Tension Meter" is an informative and interesting read (assuming you're into reading about wheel building and/or wheel maintenance).

** I'm not trying to knock Park at all, they make good tools. However, just about every bike shop crew or individual I know uses the Wheelsmith Tensiometer.