GamePart.com
Missing or replacement parts for video games and systems. Also sells some new games and hardware.
http://gamepart.com/

Game Room Classifieds
Buy, sell, or trade coin-op games, pinball machines, slot machines, and other equipment.
http://www.gameroomclassifieds.com/

Let the Game Begin
Offers used and retro games for sale and for trade.
http://www.letthegamebegin.co.uk/

PC Amusements
Buy and sell used and refurbished pinball and arcade games. Also has replacement parts for classic and modern games.
http://www.pinballs.com/

TradeLair.com
Facilitates buying, selling, and trading games as well as the exchange of hints, codes, and downloads.
http://www.tradelair.com/

Game Guys
Offers game and hardware swap for range of console systems including most current systems.
http://www.411games.com/

Used Video Game Shop Yamatoku
Nintendo Super Famicon, Sega Saturn, Play Station, Neo Geo Neo Geo from Japan Over 3,000 rare games.
http://www.yamatoku.jp/game/

VideoGameCentral.com
Retailer of used games and accessories from Atari to XBOX.
http://store.videogamecentral.com/

Nintari.net
Buy, Sell, Trade Video Games and DVDs. Includes collection management and trade matching.
http://www.nintari.net/

Gamebooklets.com
Buy or sell instruction manuals, cover art inserts and strategy guides for systems including Playstation, XBOX, Nintendo 64, Gamecube and Dreamcast.
http://www.gamebooklets.com/