Mutants & Masterminds HQ:Official game site. Features Freedom City campaign background, previews of upcoming supplements, and a message board, as well as FAQ, errata, a mini-adventure, and maps.
Arcady's Mutants And Masterminds Game: Campaign notes and general articles on the game. Features characters, story arcs, and session logs.
Brand's Brand Publications: Features free previews of Church and State, a campaign setting and adventure.
Defenders-5: Campaign setting. Includes a history and map of Pacific City, its heroes, and its villains.
Devils Workshop: Publishes sourcebooks and character archetypes in pdf format.
E-CORE - M&M Superlink News: Collects and organizes superlink information. Features articles, supers, mooks, powers and more.
Freedom City - Mystery Men: Features character biographies and statistics.
Hall of Justice: Features write-ups of DC, Marvel, and Freedom City characters.
Mutants and Masterminds: Game statistics for the Justice League.
Mutants and Masterminds - The Freedom City Game: Campaign notes that include characters, referee handouts, and session summaries.
Quantum Heroes: Alternate campaign setting featuring hero and villain write-ups and house rules.
Simpson's Excel Character Builder: Character sheets for download.
Talon Studio: Features information on Steve Kenson's game design work, including previews of upcoming projects.
The Rise of the Military Industrial Machine: Second edition campaign. Includes logs, interactive map, characters, art, and house rules.
Valdier.com: Features forums, news, and characters. Includes a character creation tutorial and a guide to buying powers.
Yahoo Groups : Mutants and Masterminds: Discussion of campaign ideas, characters, and rules.