Tampermonkey can be installed from here: http://tampermonkey.net
Once installed, click on the link below to install the script:
Click to install (v2.3.0+7dd36dfdb9acee989fef3846d19cac0b7c52a922)
Current features include:
Bookmarklets are small scripts you can run by clicking a link in your bookmark bar.
To 'install' a bookmarklet, drag the link into your bookmarks bar.