White Noise : The Hairdryer Trick for Soothing Babies
There's a certain stage a newborn baby gets to, where they're obviously tired, but have worked themselves into a state and so can't get settled.
One thing that's consistently worked for me when my daughter gets to this mood, is to plug in a hairdryer and turn it on. You don't want to point it at the baby, just have it on and in audible distance. It's amazing the effect this can have on soothing her to sleep.
Other parents I know report similar effects from the vacuum cleaner and washing machine. You can apparently buy CDs of white noise and gizmos that generate special tones, but frankly if you have a hairdryer anyway, and it works, those seem a pointless extra spend. Though they do negate the risk of accidentally burning your house down by falling asleep yourself with a hairdryer running...