What started out as a cultural exchange, has turned into a cross-country ride for charity. Saved Tattoo's Scott Campbell has been riding motorcycles for years and recently, he started taking road trips with British actor Charlie Cox (currently starring in the film "Stardust.")
After discovering a cultural difference between bikers in their respective homelands, they used it as a conceit to raise money. Basically, in the U.S., Bikers warn other riders of upcoming hazards or to slow down by dropping their left hand and extending a finger. Campbell says, it's "not to communicate distress or warning, but simply to acknowledge a mutual respect that motorcyclists share."
This past Saturday Cox and Campbell set out from L.A., planning to reach NYC by 11 September 2007. On the way, every time they see the signal Cox will give $10 to benefit a children's psychiatric hospital. If the bikers don't acknowledge them, Campbell will donate $10.
You can get more info and contribute directly to the cause on their site.