The Amazon.com/co.uk/co.jp/ca logo.  Normally, these are found on brown cardboard boxes shipped by Amazon.  On each box, there is usually one black, curved arrow, shaped resembling the mouth of a smile.

Additionally, one can find the Amazon logo on their website properties; these are usually yellow arrows shaped similar to their box counterparts.  A9 and Amazon.com both have favicons demonstrating the logo, and the page header of Amazon.com also carries the logo (amazon.com, from under the first "a" to the "z").
Amazon