I sincerely apologize for the slightly off-topic post, but I am totally going to shamelessly plug my work here.
For those interested in the Mass Effect setting, it does work very well with Saga Edition (as billd91 said). Just change The Force to Biotics, make some minor tweaks here and there to how they're used, and it completely works.
On the WotC boards, I consolidated and authored a "campaign setting" PDF (with the help/work of some very creative contributors) for the Mass Effect setting in the Star Wars Saga Edition rules. It was downloaded some 2,429 times (as of this post) and has gotten a lot of praise. It was based on the first game, included a bestiary and stats for the main characters, and even included stats for every single weapon/armor/ammo/grenade upgrade from the video game.
I am almost done working on a sweet version 2.0 of that PDF that incorporates changes to all of that gear based on the manufacturer (including Spectre gear), and streamlines/cleans up the document to make it appear more professional. I've also added a lot of content to the document and clarified a couple of things that were worded weirdly.
For those that are interested, you can PM me and I will add you to a list of people I'll send a mediafire link to containing the finished product. Heck, I might even make a post here for it if there's enough interest. Meanwhile, if you want the older one, I can still PM you a link to it if you want.
I also have a Farscape setting PDF for SWSE, and some character stat-blocks for Firefly (in PDF too). PM me for those and I'll send 'em your way.
If you want to run Firefly as a setting, just eliminate the Force altogether, and limit weaponry to slug-throwers (SWSE's name for "projectile weaponry") and daggers/swords (Vibro-weaponry isn't common). Remember that for that setting, technology is more abundant and high-tech closer to the core worlds and less available (and even extremely rare) on outlying planets.
Hope that helps!