I've recently redesigned redemption in a blog, optimizing the CSS and reducing line width for more optimal reading. I did this quickly and painlessly with a gem of a bookmarklet, the "edit styles" bookmarklet.
The "edit styles" bookmarklet allows on-the-fly editing of the active CSS file of any webpage. Try it out - click here (only in Mozilla and Mozilla Firebird - all the more reason to switch, if you haven't). Changing the CSS changes the webpage immediately, allowing for a great way to try out new styling painlessly and saving you the constant edit-reload cycle. This is a must-have tool for the web designer/developer. Drag it to your bookmark toolbar. Don't style your site without it.