National Council of Teachers of Mathematics
The Math Forum: Geometer's Sketch Pad: An Introductory Lesson
This site is a five part tutorial to get started using Geometer's Sketch Pad. The tutorial goes through things such as setting up to install GSP, the tool box, other functions, graphing,and more.
Other
Ctte: Geometer's Sketch Pad Activities
This site offers numerous activities for middle school and high school learners to explore using Geometer's Sketch Pad.