I've been meaning to post about Twitter Mosaic for quite some time now, very cool service for the community to get involved. There are two ways to get involved:-
1) With your Twitter Account (get one if you haven't got one) - add twitter_mosaic (or better known as follow twitter_mosaic).
2) Go to www.twittermosaic.com and upload your own picture to be turned into a twitter mosaic. Very likely that your picture won't be chosen.

What does Twitter Mosaic do?
It simply makes a mosaic out of twitter profile images with the pictures people upload to TwitterMosaic.

Full resolution image of end result.

Negative Mosaic of the world.

My Twitter profile image has also been used on the following mosaics, see if you can find them!
1) Soylent Green
2) Silence of the Lambs
3) Transformers