Through proficient use of a telephone, and a little bit of luck Joystiq has found out that a demo of PixelJunk Eden will be available tomorrow on PSN. It is likely the demo will only be available on the US store as Sony Europe are still asleep in regards to all things online not planning to release the game in Europe any time soon.
Joystiq comment "We just got off the phone with Sony, trying to see if we could get more info on Fat Princess, and were told that the demo for PixelJunk Eden will be available tomorrow with the regular PSN update."
If you really want to play the demo you can always create a US account to download it when it appears. However, this account won't be much good if you want to buy the full game when it releases next week (July 31st).