TSR, the Huge Game Company with Very Strict Copyright Ideas, got eaten by Wizards of the Coast, who made the most essential core rules of AD&D 3rd edition freely available through Open Gaming Foundation.
And lo! Much was another game person frightened that day! But he also thought that was a pretty cool idea.
Thus was born GURPS Lite. Last release (as of writing) was in June 23, 1999.
GURPS Lite is a free condensation of the most essential GURPS rules. This book is available in PDF format from <http://www.sjgames.com/gurps/lite/>, and also in neat printed format from many game stores (even the small local store had it along with other GURPS books). You are allowed to distribute the booklet free of charge.
The book is an excellent way to not frighten the game players. "Yes, I have an impressive array of 17 GURPS books here, and the core rules are here - " (Shows the 273-page Basic Set) " - and here - " (Shows the two thinner Compendium books) " - but, hey, you don't need to know all this! Take a look at this one - and most of this you don't need to care of, either, not at least while we're playing!"
GURPS Lite comes with some worldbooks (such as GURPS Discworld), just to let people to play without the need of the whole game...
About the contents:
GURPS Lite spends a couple of pages telling of how the game really works: Success rolls (and Contests of Skills), and reaction rolls are explained. This really doesn't take much in GURPS: The game itself is very simple, it's just that the logistics like the campaign design and character generation take all time and most of the off-session brainwork. Speaking of which...
Most of the material is about character generation; advantages, disadvantages, skills, equipment and so on. The things on the material are more than enough for getting started in most of the campaigns; If you get carried away, borrow Compendium I from the game master =)
Then, it has some words on "special" things in games (things that require more than usual attention, such as use of senses, tricky movement, and last but not least, combat.) It also has some very basic rules regarding the use of magic.
Also, the book describes the basic ideas behind GURPS game worlds.
While it's not exactly as comprehensive or liberal as WotC's d20 system, it's nevertheless interesting to give to e-roleplaying friends and other people as an introduction and a reference - and it won't cost a single eurocent to them, which is always good. =)