"Brands of the World": Downloadable logos from some of the largest companies

http://brandsoftheworld.com/
"Best brands of the World is World's one of the most visited web sites intended for browsing and exchange of the World's famous brand-logos. The primary use of site is to enable designers to access vector-forms of the well-known brand-logos that they can use in their presentations, given the permission of the copyright owner. The web site also enables designers to upload their own works and professional details."