Brands of the World
http://www.brandsoftheworld.com/
This is a great place to find just about any logo you have ever seen. Most of these are AI or EPS files which are great for scaling and printing. I do want to warn you though that these are recreated by people of the interweb. They are not always perfect, but it can get the job done if you need something quick and dirty.

Remember these should only really be used for personal use. If you have the right to use a logo then I’m sure the company would be glad to send you the official file.