Skype for the iPhone should be great http://bit.ly/skype_iphone.  With Skype on an iPhone users will be able to make VOIP calls from WI-FI hotspots instead of using their precious AT&T minutes.   There are already iPhone apps that let you do this, but an offcial Skype app will be great. This will be very interesting to watch as VOIP begins to compete directly with cellular and the mobile web becomes a reality.