The Big Friendly List of RPG rules with links and stuff...

[Knaight]

Given the current standards for popularity:

Warrior, Rogue, & Mage
A free role playing game which uses the Warrior, Rogue, and Mage archetypes as attributes. It is styled after early D&D in spirit, but uses largely modern mechanics, centered around a roll and add system with an exploding d6.

[zircher]

Gotcha covered, also updated the link to the official home page for The Trouble with Rose while I was in the neighborhood.
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TAZ

[Wordmaker]

Here's one that I've completely fallen in love with:

Hellas: Worlds of Sun and Stone - A space fantasy setting based on Greek Mythology. It's available on Drivethru RPG and well worth it! Uses the same basic Omni System as Talislanta.

[zircher]

Updated.

Here's the FtB Affliate link...
http://www.rpgnow.com/product/57436/HELLAS%3A-Worlds-of-Sun-and-Stone&affiliate_id=50144
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TAZ

[Lord Foul]

Only just checked this out again after a long time. Really impressive, Zirch.

But...

No Chivalry & Sorcery
No Runequest
No Villains & Vigilantes

Maybe they're out of circulation. I am rather old, you know.

[Knaight]

Only just checked this out again after a long time. Really impressive, Zirch.

But...

No Chivalry & Sorcery
No Runequest
No Villains & Vigilantes

Maybe they're out of circulation. I am rather old, you know.

Describe them, and they can be added.

[zircher]

Aye, it's kind of a volunteer list with comments by fellow Booters. I know that V&V is in PDF reprints, not sure about the others.
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TAZ

[Agemegos]

Aftermath! a post-apocalypse RPG, much more realistic than Gamma World, and infamously, painfully detailed and complex. Designed by Paul Hume and Bob Charrette, published by Fantasy Games Unlimited in 1981.

Bushido a roleplaying game for the Japan of legend, fantasy, and chanbara movies, by Bob Charette and Paul Hume. Published by Tyr Games in 1979, then by Phoenix Games, and finally by Fantasy Games Unlimited (1981).

[Agemegos]

DragonQuest Fantasy RPG originally published by SPI in 1980, later by Penguin and finally by TSR. Features multiple very quirky schools of magic, spells as individually-learnable skills, and a robust and tactically-interesting combat system. Apart from spells and weapons skills, each skill was a cluster of related abilities supporting an adventurer archetype. It was crunchy, but a clean design.

Universe SF RPG from SPI, published in 1981.

[Agemegos]

James Bond 007, a licensed RPG by Gerald Klug, published by Victory Games in 1983, and followed up by a a Q Manual and a series of very well-presented adventures, mostly based closely on the movies. It was a medium-complexity clean design, skill-based, and presented interesting incentives to in-genre behaviour, partly through its innovative system of "Hero Points" (a clear forerunner of Fate Points in FATE). The ingenious random encounter system produced not only Bond-movie-like incident, but also Bond-movie-like plot developments.