GameFAQs: Master System
   FAQs, codes, message boards, reviews and game data.
   http://www.gamefaqs.com/console/sms/index.html

JAG's Video Game Zone: Sega Master System
   Offers game, hardware and advertisement images and reviews plus system specifications.
   http://www.emucamp.com/jagsvgz/systems/sms/

MobyGames - Sega Master System
   List of games with screen shots and reviews.
   http://www.mobygames.com/browse/games/sega-master-system/

Richard's Sega Master System Collection
   Personal collection, accessories, action replay codes.
   http://members.citynet.net/ges/smspage.html

SMS Power
   News, ROMs, old releases, forum, and links.
   http://www.smspower.org/

SMS Tributes
   Offers game database, cheats, screenshots, reviews, and downloads.
   http://www.smstributes.co.uk

SMScene
   Reviews, technical information, emulators, game midi files, scans, ROMs, FAQs, cheats, lists, guides, history and links.
   http://www.emucamp.com/smscene/smscene.htm

Sega Master System Museum
   Game screen shots, user reviews, FAQs, hardware information and images, magazine ads, japanese game ad movies, personal collection, links.
   http://alexkidd.com

The RetroVault
   Offers cheats, downloads, and images.
   http://www.retrovault.com

UK Sega Master System Page
   History, information, specifications, a FAQ, and links.
   http://www.severedbbs.u-net.com/fletcher/SMS.html

Wikipedia: Sega SG-1000
   Information on the Sega Game 1000 includes history, emulation, and versions.
   http://en.wikipedia.org/wiki/SG-1000