Just stumbled on a very interesting project from PoolieStudios called Iconize (which in turn was inspired by this post from Ask the CSS Guy). The concept is simple: CSS code that would add little context sensitive icons next to your normal text links. If the link points to a PDF file, then add a little PDF icon next to it, if it’s an MP3 file, add a little sound icon, and so on.
What a great idea and a great implementation of CSS functionality that is seldom utilized. PoolieStudios are putting together a large collection of icons and are writing the CSS code to go along with them — you can grab the latest version here.