iKonize is a free, quick and simple way to show the file type of page links.
It can display any icon you like after a link to any type of file. It even shows external links. iKonize is written in Javascript and CSS and will work in any HTML page.

Examples

Here is a link to a pdf. Here is a link to an image. It even adds icons to links such as a word document, a spreadsheet or even an external website's file.

Download

Download iKonize version 1.0 [44kb including icons]
This software is licensed under MIT.
Silk icons provided by Famfamfam

How to use iKonize

There is a detailed article here on sitepoint.com