Documentation : Summary ( Premium Service )
Alexa® is the number one source for all rankings that help Search Engine Optimizers on a daily basis. Their information is well respected and they have been tracking since 1996. As a developer you can now use the Alexa API provided by Amazon. Amazon offers it under the name "Alexa Web Information Service" and the data comes from Alexa. This API is a passthru API meaning that you will get the raw data that comes back from Alexa's API since there's so much data nothing can be missed.
Please note that there is a charge of $0.15 per 1,000 requests ran on the system. Amazon is responsible for the billing for their service, and it will be covered when you create your account to use this API.