Source: http://www.engadget.com/2013/03/20/send-to-kindle-buttons-web-publishers-wordpress-bloggers/
Up until now, if you wanted to send content from a website directly to your Kindle for later reading, you had to install a browser extension. Now, however, you don't necessarily have to if the site in question has implemented Amazon's new "Send to Kindle" button. Made just for web publishers and Wordpress bloggers, you can already see it on The Washington Post, TIME and Boing Boing websites. Publishers can design how they want the button to look to a certain degree via limited customization of the font, color, size and theme. Like all the other Send to Kindle shortcuts, all readers need to do is select the article they want to ship over, hit the button and they'll see it on their favorite Kindle reader, be it the app or the device. Site owners can head over to the sources below to see how they can participate.
Via: PaidContent
Source: Send to Kindle for websites, Send to Kindle Wordpress plugin, Kindle Daily Post