I was pretty excited when I found out just how easy it is to add shadows to my UIViews on the iPhone/iPad.
Just add the framework in Xcode, add the import to the top
Thought I should make an answer because I didn't want this gem to get buried in the comments.
In addition to cobbal's answer above, which helped a lot, occulus also mentioned the following optimization for non-rectangular shadows, such as text shadows.
self.contentView.layer.shouldRasterize = YES;
// Fix visual degradation when rasterizing on high-density screens:
self.contentView.layer.rasterizationScale = [[UIScreen mainScreen] scale];