The Diffbot R Language Client by Diffbot provides a simple function to be used to retrieve the JSON response of URLs provided with parameters to this function. Diffbot.R file and Curl and RJSONIO R-packages are required to use this library.
For any business or website that relies on user or customer interaction, communication is important, and often the only point of contact a business may have with that customer is an email address. This is where email validation can lend a helping hand; as long as mail can be successfully sent to an address all is good, but if there's some issue causing failed delivery and other errors, better to know about it. Email Pie is a free, JSON API that provides a simple way to validate email addresses.
As announced at Google Webmaster Central, Google has released a public API to automate the usage of Google Webmaster Tools. The Webmaster Tools gives web site owners detailed statistics about their site's "visibility on Google".