Roll20 Wiki

User David G thought it'd be a good idea to start a thread with links to various resources that could be used in games.
(Taken from a forum thread - https://app.roll20.net/forum/post/289/game-resources#post-33025 )

Gaming Systems

MODERN ACTION/ADVENTURE/SPY/MILITARY GENRA -
d20 Modern - by Wizards of the Coast
Feng Shui (role-playing game)- based on Hong Kong/martial arts movies
GUMSHOE System - by Pelgrane Press
James Bond 007 (role-playing game) - by Victory Games [out of print] - based on the Ian Fleming chartacter
Mercenaries, Spies and Private Eyes - Designed by Michael Stackpole.
Over the Edge (game) - by Atlas Games
Spycraft - by Crafty Games - espionage/adventure
Modus Operandi - Espionage RPG webring - for all things spy...

FANTASY GENRE -
Basic Fantasy RPG - http://basicfantasy.org/
Dungeons & Dragons - http://www.wizards.com/dnd
Pathfinder - http://paizo.com/pathfinderRPG
Pathfinder Reference Document - http://paizo.com/pathfinderRPG/prd/

SUPERHERO / SCI-FI GENRA -
Danger Patrol - http://dangerpatrol.com
Mutants and Masterminds - http://www.mutantsandmasterminds.com/
Champions - http://www.herogames.com/home.htm

HORROR GENRA -
Call of Cthulhu - http://www.chaosium.com/
World of Darkness - http://www.white-wolf.com/

GENERIC or MULTI GENRA
GURPS - http://www.sjgames.com/gurps/
Fiasco - http://www.bullypulpitgames.com/games/fiasco/
Shadowrun - http://shadowrun4.com

http://www.opengameart.org - Graphics, Sound Effects, etc
http://www.pdsounds.org - public domain sounds - sound library
http://rpgmapshare.com - maps
http://www.d20srd.org/ - D20 3.5E System Reference Document