GMAT Institute

http://www.veritasprep.com/
http://www.kaptest.com/gmat
http://www.manhattangmat.com/
http://www.gmatpreparation.com/

Free Preparation Softwares

http://www.gorillatestprep.com/gmat_resources.html

Forums with Materials

http://www.beatthegmat.com/gmat-strategy-f3.html
http://mba-forum.4gmat.com/
http://www.scorechase.com/gmat/welcome.php
http://www.gmatxperts.com/forum.html
http://gmatclub.com/

Websites

http://www.gmattutor.com/
http://www.mba.com/mba/TaketheGMAT
http://www.gmat-mba-prep.com/

GMAT / Resources / Sections / Syllabus / Links

en.wikipedia.org/wiki/Graduate_Management_Admission_Test
http://www.beatthegmat.com/mba/resources
http://www.princetonreview.com/business/gmat-sections.aspx
http://www.veritasprep.com/s/gmat/syllabus/
http://www.educationindex.net/educationarticles/graduateschoolstips/preparegradschool/gmatbusinessexams/index.html