A CSS microscope
If you are sometimes looking at a wonderful CSS design and wonder, how this was achieved, you could look at the HTML and the CSS code and start to figure out how to achieve things. This could take quite some time.
Enter Xylo Scope.
Xylo Scope loads all CSS files, and displays the relationship between the different tags and styles. It sports something similar to the DOM explorer that browsers like Firefox have but is geared more towards the CSS aspects.
I have only looked at it briefly, but this one looks like it’s going into my toolbox. At $14.95 at a very reasonable price as well.