Measurement, Time, & The Scale of the Universe

The background music here is really annoying, but he does make quick work of the basic definitions.

http://www.youtube.com/watch?v=Iimklyw9T3U&feature=related

If your math skills are good (think sin, cos, tan…) you may be interested in this definition of what a parsec is…

Cosmic Distances & Light Speed

The Scale of the Universe
The Scale of the Universe Interactive Applet