Official Serenity RPG
Margaret Weiss Productions has released the Official Serenity RPG, using their in-house Sovereign Stone system. Reviews for the game have been mixed; while the official RPG does have a fair amount of setting detail (mostly Serenity-specific due to licencing issues), the system seems to be fairly easy, but the book is poorly edited; a lack of examples of play, rulesheets and an index is offset by the inclusion of beautifully drawn deckplans and some interesting ideas about ship and vehicle design (Ships as Characters)
Out in the Black is the first supplement realeased by MWP for the Serenity RPG. It includes several scenarios and a detailed setting of Frisco Town, on the planet of Regina.
Cortex System is an unoffical web-based community for the all Firefly-related RPG systems.
Fireflyrpg.com is home to a Serenity systems map, several very shiny deckplans, and some interesting random Firefly RPG Tables.
Dragonlaird Gaming is the personal site of Jim Davenport, one of the authors of the Serenity RPG system, and provides free information for Gamemasters.
SerenityRPG is a Yahoo Groups mailing list for discussion of the Serenity RPG.
Dogs in the Vineyard Firefly Conversion
Firefly in the Vineyard is Brandon Amancio's conversion of Firefly for the excellent Dogs in the Vineyard RPG, by Vincent Baker. The conflict resolution mechanics are especially suited to Firefly because they can start with arguments and escalate all the way up to gun-fighting. Unlike a lot of other systems, player vs. player conflicts are handled extremely well, adding to the game's enjoyment instead of taking away or bogging it down. (So when one PC has to give another a drumming-down for selling out crew-members to the Feds, perhaps using the ship's airlock to get extra dice, it totally works.)
Check out an Actual Play write-up here.
Firefly Paper Miniatures
Now available at Laurel Cadre are a collection of Firefly-based paper miniatures and Serenity deckplans. She also has some houserules for running Firefly using D20 Modern.
If you want to play this setting in the GURPS system, people are working on the conversion here.
A rules adaptation of a rules adaptation: Based on the Heroquest rules 'patch' for running Star Wars, and then further tweaked and customized for the 'Verse. Once upon a time, the rules were used to run the "Moon, Struck" campaign, featuring the crew of of the firefly-class transport Endymion.
What's better than a free rules-light RPG? A Firefly conversion for it!
A conversion of Firefly for S John Ross' Risus: The Anything RPG is available here.
There's a shiny Savaged version of the Firefly setting for the generic RPG Savage Worlds, by Pinnacle Entertainment Group/Great White Games - also the makers of Deadlands. The most outstanding aspect of the Savage Worlds rules system is that you DON'T have to put much work into Game-mastering - instead, it allows you to get right down to play: the bywords are Fast! Fun! Furious!
The Savage Firefly conversion is a very straightforward adaptation using the simple yet elegant mechanisms of Savage Worlds and just adding the Firefly flavour.
Our group plays using a slightly expanded (thanks to the Firefly Wiki!) version of the original conversion material by Jamie Herbert found here. The actual gameplay in Savaged Firefly like a lightning fast version of Deadlands in Space. You have all your Firefly action, rough humour, blasting guns, Chinese cussin' and "keepin' them flying", mixed with a Fast! Fun! and Furious! game-system that'll allow for many shiny evenings of gaming.
Did I mention roleplaying in the Firefly 'Verse is loads of fun?
Unknown Armies Firefly Conversion Uses Unknown Armies for the basic rules set for a Firefly game. The fluid skills system, the 'gritty' reality of the combat system, and even the Sanity Rules for the system just seem Firefly pretty well... all you really have to do is take out all the references to the magic system in UA and you're good to go. (River's 'psychic' abilities can be handled very well simply with very high Mind and Soul attributes and appropriate skills -- suffice it to say that River is *not* built on PC-level point totals... she's not gifted, she's a gift.)
You can check out a few pages on the subject below...
Ji Dian Station is a Firefly based LARP using a custom built rule system and a lot of information with more being added frequently. Game play revolves around the evolving story arcs created by the players and the story telling staff. The game takes place on a converted Apex class mining platform in orbit around the planet Heinlein in 2518, before the events of Serenity.
Serenity LRP is an unofficial, not-for-profit, UK-based LRP system inspired by the Serenity/Firefly universe. Rules, events details and general info are available.
So you've decided to take the plunge into a Firefly/Serenity LARP? Now all you need is to get the look down - luckily, there's a great resource available to you - Even Space Cowboys Hanker to Look Shiny
Tenth Crew Member, a regular over at Fireflyfans.net, has created a HUGE number of board and card games for the Firefly community, including BWAH! and about a dozen BWAH! expansions, plus some fighting games like Honest Brawls between Folk and a boardgame modeled after the Cargo Bay Ball Game. You can find 'em all here.
Muds, MUX and Mushes
SerenityMUSH text-based role playing game based in the 'Verse. Original characters only. Telnet to serenitymush.com port 2020.
In the Black is a Firefly Serenity 'Verse MMOFBRPG, where you create a character and choose a faction and either enforce the 'Verse as a Fed or Aim to Misbehave as a Freelancer. Its forum based so one needs to adjust to the format of writing what happens. http://s12.invisionfree.com/In_the_Black/
Neverwinter Nights - Firefly Style -- A conversion of Neverwinter Nights called Nightfire is available here: http://nwvault.ign.com/View.php?view=Modules.Detail&id=4030
Also available is a module called 'The Hero of Canton': http://nwvault.ign.com/View.php?view=Modules.Detail&id=4031
Myth-Weavers is a fully-featured forum-based play-by-post site including online Serenity character sheets, built-in dice-rolling, and a variety of other tools to make your Serenity RPG story flow smoother than platinum into the hands of drops-dealer.