Auto-reformat Web articles for easier reading: Readability (free)
Get it here. It’s free.
UPDATE: Some serious issues with Readability: rip-off artists, I see. I have been using Instapaper.com, which puts a button in my browser “Send to Kindle” and will also save articles (i.e., titles and links) on my page at Instapaper.com, so I can easily return to the article. I found Readability only this morning, and based on the information at the link, I’ll return to Instapaper for when I want the article, and use Readability only for on-screen formatting.
Thanks to John Anthony Grigutis for pointing this out. (See comment.)