Fivefilters.org has an extension/webpage for sending webpages to your kindle. However, you have to wait for it to fetch the page, then press 'send' and then wait for it to send, before you can close the now redundant window.

This script automates the whole process, including closing the browser window. I often send multiple web pages so this saves a lot of bother.

Instructions:

It won't work until you've filled in the kindle email address on the fivefilters webpage, however; and if you need to change that, then you'll need to disable the script because you won't have time to do it before it sends and closes.