ModMyiPhone posts two claimed leaked screenshots of the iPhone's upcoming iTunes App Store.
He was just bored pressing buttons on his phone and suddenly instead of getting the normal "cannot connect" message that he had previously encountered, appstore launched revealing the appstore UI. Browsing around he found that the Genres and Top 50 categories contained a few apps.
The screenshots aren't necessarily telling from a user's perspective. In this regard, Apple gave a more comprehensive preview during their SDK press event.
The images are also being hosted over at TUAW.