8GB or so is photos. I like to have all the photos I've ever taken on an iPhone on hand and leaving the full size ones in the photo roll is easier than messing about with syncing.

I write apps as part of my job, so part of having so many installed is as I trying lots of stuff out from the App Store just so I keep on top of what people are up to.

Also, about 2GB of the 15GB of apps is UK and European TomTom and probably two thirds of the rest is made up of a handful of large games.