Something tells me this site is doing something wrong (http://www.brandsoftheworld.com/search/), but for anyone who's needed a logo for a presentation, it seems like manna from heaven. Type in the name of the company for which you need a logo and it returns a list of possible matches. I tried a random list of companies like ESPN, AON, Caterpillar, and Quaker Oats and it had them all.
Sure, you could try going to all the different company Web sites to get them, but Best Brands of the World has them in .EPS format, which beats those fuzzy web logos any day. Plus, some sites are very careful not to make their logo easy to download and use by mixing it with other graphics or slicing it into pieces.
Happy logo hunting!