I have a friend who works for a company that makes software for the BlackBerry. He's an OS X nut and has got a few people there to start using Macs. In his spare time he has told me he is working on a way to sync up a BlackBerry with iSync. Not sure where he is at, but I will try to check with him.
Would be really nice. If it worked. Apple kind of shot themselves in the foot with RIM.
RIM is not very far from where I work. RIM wanted to support Apple and the Newton when they were just making wireless cards. They bought several Newton MessagePad 2000's. They had to wait forever for Apple to ship the weird little dongles they had and some extra accessories. When they finally shipped and they were going to get started, Apple pulled the plug on Newton. A high up engineer told me personally, "no one is ever going to support Apple if they pull stunts like this... no warning or anything. We certainly won't." So getting RIM to support the Mac may be an uphill battle.
Maybe it's a good thing that RIM has changed a fair bit over the past couple of years. Maybe the people that got burned working with Apple in the past are off doing other things, so RIM might feel more inclined to work on Apple software (especially if it's as simple as an iSync plug-in).