National Council of Teachers of Mathematics
The Math Forum: Drexel University: Math Forum: 3 D Drawing and Geometry
Instructions on a simple way to get started drawing in 3-D by drawing objects using an isometric grid.
CK-12 Foundation
Ck 12: Geometry: Representing Solids Study Guide
[Free Registration/Login may be required to access all resource tools.] This study guide gives an overview of isometric view, orthographic view, cross-section, and nets.