e-Source: Chapter 4 'Concepts in Sample Surveys' by Sarah M. Nusser and Michael D. Larsen
all at:
www.esourceresearch.org

Probability and Non-Probability Sampling
www.tardis.ed.ac.uk/~kate/qmcweb/s2.htm

Sample Size Calculator
www.surveysystem.com/sscalc.htm

StatPac – Survey Sampling Methods
http://www.statpac.com/surveys/sampling.htm

StatTrek – Introduction to Survey Sampling
http://stattrek.com/Lesson6/SurveySampling.aspx

SlideShare – Sampling in Qualitative and Quantative Research
http://www.slideshare.net/sladner/sampling-methods-in-qualitative-and-quantitative-research-presentation