Popular can have many interpretations. Due to the amazing success of the Drive-Thru RPG Haiti bundle, dozens of little or unknown RPGs now have circulation in the thousands. I went through the bundle and I think I have a pretty complete list of those RPG and I plan to look over them all. (Of course, any other buyers of the Haiti bundle or owners/players of the following games are welcome to write up something as well.)

Some of these titles are already on the main list, but I'm post the RPG list here for completeness sake:

Apocalypse Prevention, Inc.
http://www.thirdeyegames.net/

Barbarians Versus
http://www.mysticages.com/games/bv/index.htm

BASH! Basic Action Super Heroes (Original Edition)
http://www.bashrpg.com/

Beast Hunters RPG
http://www.berengad.com/bh/

Blood Games II
http://www.flyingmice.com/bloodgames.html

Chronica Feudalis
http://jeremykeller.com/category/chronica/

Classic Spycraft: Spycraft Espionage Handbook
http://www.crafty-games.com/product_catalog/classicspycraft

Cortex System Role Playing Game
http://www.margaretweis.com/mwp-online-store/cortex/23-cortex-system-role-playing-game

Damnation Decade
http://www.greenronin.com/store/product/grr1411e.html

Diana: Warrior Princess
http://homepage.ntlworld.com/forgottenfutures/others.htm

Ephemeris
http://www.nomadicdeliriumpress.com/ephemeris/main.htm

Full Light, Full Steam
http://kallistipress.com/category/my-books/full-light-full-steam/

Karma Roleplaying System Core Rules Book
http://www.bardsandsages.com/karma

Kids, Castles & Caves
http://bravehalfling.com/

Labyrinths & Lycanthropes
http://www.princeofdarknessgames.com/L&L/index.htm

MADS Role Playing Game
(no publisher link found)

MARS: Savage Worlds Edition (need to confirm if this is a full RPG or a settings book)
http://www.adamantentertainment.com/

Piledrivers and Powerbombs: Chokeslam of Darkness Edition
http://www.princeofdarknessgames.com/PnP/index.htm

Privateers and Pirates
http://www.fjgaming.com/pages/games/privateers-and-pirates.php

QAGS Second Edition
http://www.hexgames.com/qags/component/virtuemart/details/1/10/all-products/qags-second-edition

Roma Imperious
http://roma.hinterwelt.com/

Serenity Role Playing Game
http://www.margaretweis.com/mwp-online-store/serenity/21-serenity-role-playing-game

Seven Leagues roleplaying game of Faerie
http://www.malcontentgames.com/7L/index.html

Shambles
http://aterribleidea.com/shambles/

Summerland Revised and Expanded Edition
http://stores.lulu.com/grexx

Tales of Wyn D'mere Role Playing Game!
(no publisher link found)

The Black Spot
(no publisher link found)

The Squared Circle:Wrestling RPG
http://www.daydreamerinteractive.com/squared_circle.html

The Veggie Patch
http://www.polgarusgames.com/download-page

Three Sixteen
http://gregorhutton.com/boxninja/threesixteen/index.html

Valherjar: The Chosen Slain Core Rulebook
http://www.gmpress.com/valherjar/index.html

Wayfarers
http://yeoldegamingcompanye.com/wayfarersmain.htm
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TAZ

Yeah, if you played a one shot of each RPG every month (not counting the adventures and setting books), you would have years and years of gaming material.

Added API and struck out those RPGs on the Haiti list that are already in the main list on page one.
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TAZ

The author of Blood, Sweat, and Steel stopped by to provide some links, will add them in a second.
--
TAZ

More updates planned tonight. Note to self, buy...

Remember Tomorrow
http://gregorhutton.com/boxninja/remember/index.html

Download...

Ghost/Echo (two page RPG?)
http://www.onesevendesign.com/ghostecho/
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TAZ

Added Barbarians Versus, Ghost/Echo, and Lacuna Part1.

My advertising here is done.

Well, probably not, it still remains a good example for game design discussion.

Note to self, add write up and links to Broken Gears (d12 animistic steampunk).
http://www.r-hansen.com/broken/--
TAZ

Added Broken Gears and Everyone is John.
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TAZ

I personally think this is a great post because I am constantly amazed at how many gamers I meet that have never played anything but D&D. Even other podcasters... they should know better!

Game design is one of my hobbies, so I'm a voracious reader of game rules of all kinds.
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TAZ