Not sure about you, but I find that the best way to send our chief tester off to sleep is to play her a lullaby. Well one company, seeing that most gadget lovers have iPods rather than portable CD players has created the iCrib.
Insert you ipod, hang it on the crib and off you go.

The iCrib features two speakers, a volume limiter and a night light to sooth your little one. There is also a timer that allows you to play 15, 30 and 60 minutes of music before it turns off so you don't bored them with 5 days of classic lullabies or Mozart (delete as appropriate).

Of course although designed for the iPod the unit actually takes any MP3 player and the whole unit attaches on to any crib via some Velcro straps.

Available from Munchkins.com in the US, the iCrib should set you back around $30.