Just one day after I write about the first solid mashup using the Digg API, today brings an even better one.

Derek van Vliet has created a Firefox extension that sits at the bottom of you browser and lets you know if the site you are viewing has been dugg and if so how many times. A click of this will take you to the Digg page for the site, or if it hasn’t been dugg yet, it takes you to the submission page.

This tool is so great that I simply cannot believe Digg themselves didn’t come up with this at any point over the past couple of years. Imagine the number of duplicate submissions that can be stopped if users simply install and pay attention to this extension.

It also should help more diverse content find it’s way to Digg because it’s so simple and unlike a bookmarklet, it tells you right there if the story has already been submitted, so you don’t need to click and wait to see the results (unless of course someone submitted the rss link or some variation of the main URL already).

Muhammad has more on it at Pronet.