Okay:

Nikon 5900: 150g (without battery)
Canon SD400: 130g (without battery)
Nikon S1: 118g (without battery, and $360 at B&H)

My dad has the Nikon 7900 (same camera as the 5900 but with 7 megapixel sensor). It fits handily in a pocket. If you really care about those extra 20 grams, then there are a variety of other cameras in the same price range as the SD400. Personally, I'm most intrigued by the brand-new Casio EX-S500 or Panasonic Lumix FX8 which both have image stabilization built in. I'm toying with getting something along these lines to toss into the diaper bag so we've always a semi-decent camera with which to take gratuitous baby pictures.