The latest edition of Wired (not yet on the web), has an intriguing little article on the mystery of UVB-76. UVB-76 is apparently a transmitter in or around Russia that generates a smattering of buzzes and blurbs, and has been doing so for decades. The purpose of the transmitter< is unknown, with theories being suggested from the mundane (used for testing equipment) to the exotic (used by Russian spies). The whole thing is just one big fun mystery.
I'm not sure quite what I find so appealing about it - probably the mix of relatively low tech (short-wave radio) hardware and the big impact it's having (in terms of the imagination being captured). It's worth reading up about, and when the Wired article does appear online, it's definitely worth a read.
In the mean time, you can listen in on the feed here. Perhaps it's just the right blend of white noise you need to put your little one to bed?