A computer professional certification can be the doorway to opportunity. Learn about options, and courses, from About.com.

Provides practices tests, study guides and online learning courses to help IT professionals prepare for most certification exams.

IT professional shares his collection of links to free study guides, practice questions, and other resources and offers advice to help others studying for the certifications he has earned.

Certification tutorials by Jeremy Reis

Offers accreditation for security analysts (OPSA), security testers (OPST), and Open Source Security Testing Methodology Manual (OSSTMM) specialists (OPSS).

Offers study guides, practice tests, and articles for certification exams.

Makers of practice tests for certification exams. Offers free demo downloads.

Exam simulation software for Cisco, Microsoft, CompTIA, Oracle, EC-Council, Check Point, ISC2 and Sun exams.

Provides practice tests for most major vendor certifications.

Sells training kits for students interested in practicing for various certifications.