What iPhone data is backed up by iCloud?

iCloud automatically backs up your iPhone data, but what exactly is uploaded to Apple's servers for safekeeping?

iCloud backs up and gives you unlimited space for:
Purchased music, apps, books, movies and television shows. Previously purchased items may not be restored if the item is removed from the store.

iCloud backs up and allows 5 GB free storage for:
App data
Home screen icon layout and folders
iOS Settings (including Calendar accounts, Contacts, Favorites, Mail and Wallpaper)
Messages including iMessage, MMS and SMS (text messages)
Photos and videos in the Camera Roll
Ringtones

These items are not backed up using iCloud and must be backed up using iTunes on a computer:
Music or other media not purchased from iTunes
Photos originally synced from a computer
Podcasts and audio books