The GED
The GED is the equivalent of a high school diploma. The GED has certain requirements to take that vary state by state, and the simplest way to find them is by contacting your local testing center. The GED is recommended for all homeschooled/unschooled students and students who elect to drop out of school.
GED Test Study Guide - A useful guide for the GED test.
GED Testing Service - Contains information regarding the GED test.
GED Test Review - Contains a brief overview of the test.
McGraw-Hill's GED With CD-ROM (Amazon.com) - A comprehensive study guide for the test.
Find a GED Testing Center - A search engine that will turn up all testing centers within you zip code.