The Verge - The logo rotates 90 degrees on hover to indicate “Back to top.”
Sounds Just Like - Play a song and the logo vibrates to the music.
Boxee - When not connected to the Internet, the Boxee logo goes orange and starts sleeping.
/via Emil Tullstedt
Akismet - When you right click the logo, it shows you a dialogue offering you different high resolution versions of the logo.
Dailymotion – the logo in the videos’ corner acts as a timeline, becoming more opaque from left to right.