University of Colorado
University of Colorado: Error, Accuracy, & Precision
A serious paper by serious geographers, discussing at full length the problems caused by error, inaccuracy, and imprecision in Geographical Information Systems. The definitive word in the real world.
Other
Artel: Lab Report 4: Defining Accuracy, Precision, and Trueness
This maker of precision instruments presents this solid article on the topic of accuracy and precision. Great discussion of types and sources of error, and quality control.