Twitter …… Pico Alphabet (Modified)
Digg …… FFF Forward (Modified)
Last.fm …… National (Modified)
Flickr …… Frutiger Black
YouTube …… Alternate Gothic No. 2
Facebook …… Klavika (Modified)
Engadget …… Engadget Font (Close Match)
Google …… Catull BQ
Yahoo …… Yahoo Font
Skype …… Helvetica Rounded Bold