This tweak works only on your desktop browsers. You need to download and install an extension called TamperMonkey for Google Chrome from here. On Firefox, you can use GreaseMonkey, but I need user feedback about whether the script works there or not.
Once you’ve installed the extension, go here and copy the script. Click on the TamperMonkey icon in Chrome and hit Dashboard, then hit the Add Script icon (small script icon with plus sign) and replace the text with the script you’ve just copied.
Hit Save (or press Ctrl+S / Cmd+S) and it’ll prompt you for permissions to run this on all Facebook domains. Once you give it permission, you can refresh to a cleaner, more useful Facebook.
You’ll notice that the side ‘feed’ is gone. You can now drag the chat window up and it’ll take the entire right side of the window. Facebook will remember that size when you come back later. Enjoy FB Cleanse!
Update: The folks up at Facebook are super sneaky! They push out the sidebar elements after the page finishes loading. So I made a change to the script to run every few seconds and remove the bad elements. If you have not done so, pull the new script from the above link and replace the old one.