Despite the efforts of web designers everywhere, the internet is still full of badly-designed websites that frustrate readers. Over-crowded content areas filled with widgets, overloaded moving banner ads and the dreaded 5-page article that could easily fit on one; you probably run into at least one site that is genuinely unpleasant to use in a day.
For those situations, which thankfully don’t come up as often as they used to, there is a nifty bookmarklet called Readability (incorporated into Safari 5 as Reader). Activate the bookmarklet on an annoying page and watch it be instantly reformatted into an elegant content-only view with no distractions. It should even crawl multi-page articles and put the whole article on one page.