Is your phone jailbroken? Cos thats where your jailbroken apps and data shown up in iTunes. iTunes doesn't know what that data is (as obviously it doesn't support jailbroken apps and info) so it just shows it as other data. It's also where your operating system etc is stored, and I think your camera roll is there too (the "photo's" bit I think is for photo's you've synced over, not the camera roll)

If it's not jailbroken, then I don't know why you have 1.7gb of "other"