Outrageous

Old meaning: causing public outrage, like a serial murderer or child-molester.
New meaning: In quirkily bad taste, like appearing slightly drunk at the Golden Globe Awards.


Awesome

Old meaning: awe-inspiring, like the Grand Canyon, or the launch of an Atlas missile.
New meaning: convenient, like receiving a coupon for a free liter of Coke.


Incredible

Old meaning: Inspiring disbelief or mistrust, like a failed political speech.
New meaning: Inspiring belief or trust, like a successful political speech.


Infamous

Old meaning: Egregiously evil, like Hitler or Pol Pot.
New meaning: Famous for showing one's naughty bits, like Paris Hilton or Brett Favre.