My first post of 2012 should be considered slightly off-topic but I thought it was still worthy of a share as an example of visual explanation. I really like the idea behind the new "50p Sports Collection" released by the Royal Mint to commemorate the 2012 London Olympics. A competition was run to invite special coin designs to be released for each of the sporting events taking place and I was especially drawn to the winning coin design for football.

As you can see from the close-up image below, designer Neil Wolfson has chosen to use the design space provided to graphically explain the offside rule. As any football fan will know, articulating this most contentious of laws is one of life's most recurring and often fruitless challenges.

Sure, it doesn't quite cover every nuance of the official FIFA rulebook (page 33 if you're interested) but it is a novel solution to this design challenge.
Best of the visualisation web... December 2011 (part 1)
10 significant visualisation developments: July to December 2011