Yes, fortunately it does. The iPhone is equipped with a connectivity port just like that of the iPod. This means that the iPhone will connect to existing iPod accessories like car docks and speaker systems.
On your iPhone, when the iPhone is released and you go buy the iPhone at a licensed Apple or Cingular retail store.
Just kidding. We found a nice, high quality version right here (and it's free):
Update: See this FAQ to make custom ringtones using iTunes.
At this time, the only way to use custom ringtones on the Apple iPhone is through a somewhat complicated hack.
Apple is rumored to be planning custom ringontes for a coming update to the iPhone.
No, not when the iPhone is released anyway. This is most likely because Cingular fears possible bandwidth issues. An Apple spokesperson suggested that it would be technically possible to add the iTunes software in the future. It is not known at this time if first generation iPhones will be able to be updated with the iTunes software or if it will be a nextgen addition.
The operating system will be stored along side your music. On the bright side, Apple claims that the iPhone's version of OS X should only take up less than half a gigabye of space. So in reality, it appears that iPhones will have 3.5 and 7.5GB of free space to work with.