From comp.fonts via Google Groups
The font used for the Google logo is Catull that has been 3D’d with some graphics program. Catull is a Berthold font and Adobe, Berthold, Precision Type and others sell it. This page has links to places that sell typefaces: http://bowfinprintworks.com/providers.html More info on Catull: Designer is Gustav Jaeger / Publisher is Berthold Types Limited.
According to Neowin Forum, alternatives to Catull are Batang, MS PGothic and Book Antiqua. Special Google Holiday Logos and the official Logos. Everything you always wanted to know about Google is on the Google Weblog. And here is a eMule link to this font: Catull.-.the.google.font.zip