The Google Quick Reference (see link below) lists some of the more advanced operators you can use. I especially like the following:

  • old units in new units: for example 100 euros in forint or 7.6 feet in meter.
  • filetype:<type>: for example javascript guide filetype:pdf for javascript guides in pdf format.
  • movie:<movie name>: for example movie:King Kong for movie reviews of King Kong.
  • define:<term>: for example define:blog for a definition of the word blog

Check out the guide for more examples.

Google Guide Quick Reference