dpreview.com has added a camera feature search, so you can search their database for cameras
that have a specific feature. One 'feature' that you can search is camera weight.
then click 'Show advanced search filters'
click on 'Weight' under Physical.
set the slider to the weight range you seek.
For example, there are 4 cameras in their database that weigh less than 100 grams:
the lightest is the Samsung ST30 at 87 grams. If you click 'include discontinued',
you also get to see discontinued cameras in their database.
There is a 60 gram discontinued camera, but it's only 0.3 megapixels.