Most of these apps are also suitable for the iPod touch.
1. Facebook
The world's biggest social network brings a tightly honed experience to the iPhone and iPod touch, but nonetheless still enables you to access your contacts, feeds and other important information. This sense of focus makes it in many ways superior to using Facebook in a desktop browser.
Facebook

2. PhotoSynth

We did a bit of a double-take on seeing Microsoft's name attached to this,