This is an ongoing collection of great examples of responsive websites, in no particular order:
bostonglobe.com
anderssonwise.com
css-tricks.com
greygoose.com
2012.newadventuresconf.com
heathlife.co.uk
londonandpartners.com
oliverrussell.com
rourkery.com
ethanmarcotte.com
unitedpixelworkers.com
trentwalton.com
jackdaniels.com
m.bestbuy.ca
people.com
starbucks.com
Responsive Design Resources
designinfluences.com/fluid960gs – 960px grid system