Required Materials:

Coast Pilot:

U.S. Coast Guard Captains License Exam Database:

Another database of questions:

Exam Illustrations:

From my research, here are the top five online test prep schools:

Joel's recommend book - its a one-stop shop to prep you for the test and includes a great CD-ROM with test questions:

Get Your Captain's License, Fourth Edition
Amazon Price: $38.33
List Price: $69.95