iPhone 4? Check. Protective case? Check. Now it's time to really start enjoying your new phone. We have no doubt that you've already started to splurge on apps for your new toy, but we want to make sure you're using apps that take full advantage of the iPhone 4's new high-tech functionality like multitasking, its awesome retina display, and 720p video recording ability. We collected five apps we think you should download immediately if you haven't already. Thank us later.