Stumbled upon this excellent little resource called
The GMAT Demystified by
Aristotle Prep (guys who make the SC and CR Grails)

. Great introduction to GMAT and some wise tips and pointers. Clearly not as exhaustive and detailed as the
MGMAT GMAT Roadmap, but does well to bring someone new to GMAT up to terms real quick (and hey, its free!). You can download the ebook from below.
P.S. : I have already sought permission from Aristotle Prep to post the ebook here.

Excerpt from the website:
If you are just kicking off your GMAT preparation, this 25 page ebook is the book to start with. Not only does this book help you become familiar with the basics of the GMAT, but it also provides you insights and strategies that to score better on the GMAT. This book doesn’t teach you any concepts for the GMAT- it will not teach you sentence correction rules or critical reasoning strategies, but it will help you align your preparation in such a way that you are able to achieve your target score.
Table of Contents
Part –I : Introduction
1. Getting Started …………………………………….………………..7
2. The Pyramid of success on GMAT …………….………………….13
3. Visualizing Success-The Key to Stay Motivated …..…..…………14
Part-II : Advice, Tips, Insights that you will not find elsewhere
1. The wrong and the right way to prepare for the GMAT………….16
2. Debunking some myths……………………….…………………..18
3. Five Incredibly useful tips for the GMAT ………………………….21
Part- III: Getting ready for the test day
1. Three things to do before the GMAT………………………………22
2. Three things to do on the GMAT ……….………………………….22
3. Three things to avoid on the GMAT ……….……….……………23
Part- IV: How exactly do they differ?
Difference between a 760, 700 and 600 scorer…………….………….24
Hope this helps