Modern and Espionage

Delta System
New rules and skills, a campaign based on the manga Appleseed and another set in a world savaged by extreme natural forces and torn by a great war, for the Delta Force system.
http://www.vampyreweb.com/rpg/delta/

Mercenaries, Spies and Private Eyes
A contemporary system in which the players are flinty mercenaries, suave spies, and gumshoe detectives.
http://www.flyingbuffalo.com/mercen.htm

The M.I.B. Files
New Aliens, Monsters, Gadgets, Vehicles, and Characters for West End Games' Men in Black roleplayng system.
http://www.geocities.com/men_in_black_USA/

Modus Operandi
Articles, NPCs, downloads, forums, news, and scenario hooks for various espionage systems.
http://www.modus-operandi.co.uk/

National Security Decision-Making Game
The NSDM Game recreates real-world international crises of the present or immediate future. Ideas for scenarios are taken from current headlines and developing trends. Players take the parts of national leaders, dignitaries, ambassadors, military leaders, and political groups and are given the opportunity to try and solve all the world's problems. Played only at gaming conventions.
http://www.nsdmg.org/

PCCS Unofficial Support Page
House rules, new weapons, and links for Leading Edge Games' "Phoenix Command".
http://www.phoenixcommand.com/

Web-Grognards: Commando
Variant combat and character-generation rules for SPI's roleplaying game set in World War II. [PDF]
http://grognard.com/variants/commando.pdf