This is a pretty cool demo video. I had not even heard of Seadragon before, but I am not going to forget about or Photosynth now :)

http://www.ted.com/index.php/talks/view/id/129

You also need to check out TED:

http://www.ted.com/index.php/

Here is a different one.  At eSnailer, you can compose a message and send it through postal mail, no stamp required!

Yep, there is a catch as usual, you have to select ads to include with your letter.  Cool idea thought to get ads pushed through the front door of someone's house, bypassing the typical human junk mail filter to the trash bin...

http://esnailer.com