Readability

"Readability - An Arc90 Lab Experiment is a simple tool that makes reading on the Web more enjoyable by removing the clutter around what you're reading."

I've been playing with it for a few months. I didn't use it much at first but I've used it a bunch in the last couple of weeks. It definitely works much better than just increasing the text size via your browser.

You customize the style, text size and margin width and then drag a bookmarklet to your toolbar. Then on whatever page you're reading, just click the bookmarklet and it will reformat the text on the page. It's great for reading long articles and removing the clutter of side articles, links and ads (if you don't already use an adblocker, I'm using GlimmerBlocker on the mac). To undo it, just reload the page.

A few weaknesses. It doesn't automatically convert from multiple page articles to all-on-one page viewing. You probably want to do that first before reformatting the text. Also it doesn't include images, even if they are part of the article (like graphs).