We've been hearing rumors that the iPhone is headed to Verizon since just about when the original iPhone made its debut in 2007.  What we haven't heard as often is that the iPhone would be headed to Sprint, but that's exactly what the latest rumor seems to be.  MacRumors has received a couple of tips from sources affiliated with Sprint that have said that the iPhone will indeed be available on the No. 3 carrier later this year.  One of those sources went on to say that the device would be available on Sprint around September, which is approximately when the iPhone has been rumored to be headed to Verizon, as well.  While there's no way to tell if any of these rumors are true until we hear it directly from Steve Jobs, I'm sure that Sprint would love to have the iPhone, as their CFO Robert Brust has stated in the past.  It may not be Verizon, but there would probably be quite a few people that would leave AT&T for Sprint and their considerably cheaper monthly plans.  When September rolls around, we may finally see the iPhone available on several carriers, perhaps even all of the big four, which would definitely help Apple and the iPhone compete with Android.