It's almost a year since we launched the Challenges system on and we've been constantly impressed with the quality of submissions and the imagination of the challenge hosts. To showcase this talent and imagination, we're running a 'Challenge of Challenges,' to find the Picture of the Year. All previous challenge-winning images have been automatically entered and voting starts immediately so, if you've been as impressed as we have, make sure you show it by helping to choose 2009's best challenge-winning image.

Click here to explore and vote for the best challenge-winning images of 2009