More than 20 years ago, one man took it upon himself to raise money to support the efforts of the American Cancer Society. Today, more than three million Americans participate in Relay events nationwide.I pinched the above from the American Cancer Society's webpage. It sums up what RFL is for pretty well. The things I'm about to mention being in Second Life doesn't change that.
I know of it from being a member of Caledon (if not a grounded resident) since my earliest days in Second Life. How that came about, I have no idea. But last year (and I presume the one before), they made a big Caledon team and tried to raise a whole bunch of money through SL for the cause. Same deal this year. It is generally done by selling items made just for the occasion, charity balls, and so forth.
Being british, it isn't especially important to me, although anything for Cancer Research in general has to be worth the thought.
See, below, the items I bought from Euterpe Luik, an obviously talented creator to manage both a rapier and necklace!