Bonjour, you can uninstall it.
Apple Mobile Device Support, you cannot uninstall it if you want to sync your ipod/iphone.
Bonjour is a client interface for discovering services on the local area network. For most windows users it is not THAT useful. For a list of features provided by Bonjour please have a look at the wikipedia. Below is a short excerpt:
Bonjour is a general method to discover services on a local area network. It is widely used throughout Mac OS X and allows users to set up a network without any configuration. Currently it is used to find printers and file-sharing servers. It is also used by iTunes to find shared music, iPhoto to find shared photos, iChat, Adobe Systems Creative Suite 3, Proteus, Adium, Fire, Pidgin, Skype, Vine Server, Elgato EyeTV to share local recordings with multiple clients, the Gizmo5 to find other users on the local network, TiVo Desktop to find digital video recorders and shared media libraries, SubEthaEdit and e to find document collaborators, Contactizer to find and share contacts, tasks, and events information, and OmniFocus to synchronize projects and tasks across the Mac desktop and the iPhone or iPod touch. It is used by Safari to find local web servers and configuration pages for local devices, and by Asterisk to advertise telephone services along with configuration parameters to VoIP phones and dialers. Software such as Bonjour Browser or iStumbler, both for Mac OS X, or Zeroconf Neighborhood Explorer for Windows, can be used to view all services declared by these applications. Apple's "Remote" application for iPhone and iPod Touch also uses Bonjour to establish connection to iTunes libraries via Wi-Fi.