For all those who suffer from "foot-in-mouth" syndrome, Something Awful has prepared an awkwardness survival guide! Here's an excerpt:
You lean back too far in your chair and almost fall over.
In a moment of idleness, you decide to create the mildly euphoric sensation of leaning back on two legs of your chair. You lean too far, and nearly fall over backward; you catch your balance after some amount of flailing, and the front legs of your chair land on the ground with a loud thud.
We're hesitant to recommend faking a seizure to avoid awkwardness, mostly because its overuse is dangerous. If everyone became aware of the possibilities of the fake seizure, not a single social event could occur without at least a dozen fake seizures; they would become so commonplace that real seizures would go untreated, and thousands of epileptics would die every year from swallowing their tongues.
However, in this case, we recommend falling out of your chair and faking a seizure.
Link - via Andy's Blog
Do it with a straight face and any awkwardness is quickly transfered to the other people as they have to figure out how to deal with what they just experienced.
If someone sneers at you, mutter "barbarians" and something about performance art.