Denon's AV receiver has built-in AirPlay, outstanding sound quality and six HDMI inputs--what more could you want? It's an excellent gift for the home theater enthusiast looking to upgrade the centerpiece of their home audio system.
If the Denon AVR-1912 isn't your style, the Pioneer VSX-1021-K is a great alternative. It also has built-in AirPlay, plus a bunch of unique iPhone and iPad apps you can use to control the receiver. The onscreen display is also one of the better ones we've seen.
If you're into AirPlay, the Apple TV is the product to get. It's the only AirPlay product we've seen that supports both audio and video, plus its $100 price make it one of the most affordable options available.
This isn't a value pick, but the holidays are a time when you might be willing to splurge. The B&W Zeppelin Air is one of the better AirPlay-compatible speakers we've heard, with a truly unique design and solid sound quality.