I've heard excellent things about the game "Savage Worlds" by Pinnacle Entertainment Group. It looks to be a very rules-light, setting-heavy game which plays very fast and relies a lot on the game master to resolve potentially complex situations with the very minimalist rules systems that it provides. Sound familiar?
I bought the rulebook today and have spent much of the afternoon reading through it. One enterprising fellow over on Pinnacle's web forums (curiously called the Great White Games forums, a company which is mentioned in the rulebook but whose relationship to Pinnacle seems to be somewhat nebulous at first glance) has already set about the task of converting Greyhawk to the SW system.
I've not actually played or GM'ed the system, so I cannot pretend to give a review here. But based on what I've seen in the rules, I like it. It gives the GM a lot of freedom, but under the rubric of a generic and universal system. It's not class-based at all, and the leveling system is rudimentary, but that's intentional. After all, the designers were going for quick and adaptable, not trying to make a 0E/1E emulator. And yet, in taking the approach they did, they do seem to have captured some of the wide-open feel of the very oldest games. My inner jury is still out, and I doubt that I'd use this particular system for Greyhawk (which, to my mind, wouldn't be the same without a Vancian magic system and a more developed leveling structure, which seems to be necessary for the sort of megadungeon environment that Greyhawk embodies), but I might well find this an ideal system for some other games I've had lurking about in the back of my mind. I've been wanting to do a wild west game ever since I saw "The Magnificent Seven" for the first time a couple of months ago. And a mafia-like crime game. Mad Scientist Tries to Take Over the World seems like a natural for this game.
Those, of course, would be limited in scope, rather than years-long campaigns. And maybe that's the best fit for something like Savage Worlds. When you need a break from (or something to go alongside) your traditional game of choice, the plethora of settings and adventures available for Savage Worlds might be just the ticket.
Plus it's got a wide-open license for fan products that are not sold for profit. Seems like they're pretty lenient with for-profit professional licenses, too, as long as they have decent production values. I like that sort of corporate spirit. They gave one to the Evil DM, as a matter of fact!
I might very well put a game together in some non-fantasy genre. If and when that happens, I'll report back here.