Greasemonkey is a Firefox extension that allows you to customize the way webpages look and function.
Hundreds of scripts are already available for free. And if youre the tinkerer sort, you can also write your own. More Info »
Greasemonkey is also a platform with 4 apps listed on AlternativeTo. Browse all 4 apps for Greasemonkey
You can add these Widgets to your site if you want to promote your app on AlternativeTo. Just copy the code right next to each box and then paste it on your website.