DJ Riko's "Whistler's Delight" is a mash-up that mixes together dozens of songs in which part or all of the action is accomplished through whistling -- Andy of Mayberry theme, Sweet Georgia Brown, Dock of the Bay, Whistle While You Work, and so on. Twenty-two songs in all, expertly pitch-bent to the same key and mixed together. I'm really digging it. 8MB MP3 Link (Thanks, Matt!)
Update: Spike provides this torrent for Whistler's Delight -- thanks, Spike!
Update 2: DJ Riko himself provides this alternate direct download link