MediaBistro has a “Brands of the World” website that is amazing.  This is a database of what must be thousands and thousands of logos.  What’s even more amazing is that these logos are not bitmaps but rather .eps or .ai files, meaning that the vector information will give you as high of a resolution as you wanted.

A great website if you are looking for ideas for logos or if you are designing something for an event with corporate sponsors.

As an aside, if you are looking for more logo inspiration, one of my favorite websites is Creattica.  It is a place for designers to show of their latest work.  They have galleries for business cards, websites, and other graphic art forms as well.  Go check it out.