Reference Topics 14-3

This site is a glossary of statistical terms:
http://www.stat.berkeley.edu/users/stark/SticiGui/Text/gloss.htm

This excellent site presents a tutorial over several measures of dispersion: range, percentile scores, quartile scores, variance, standard deviation, and z-scores.
http://simon.cs.vt.edu/SoSci/converted/Dispersion_I/activity.htmlSee the whole entry