Firefox only (Windows/Mac/Linux): Add-Art is a unique advertisement-blocking solution for Firefox. Instead of simply deleting ads from the page, it replaces them with art by featured artists.
The open-source project was inspired by the popularity of ad-blocking Firefox extensions—Adblock Plus, the perennial Lifehacker favorite, is downloaded over 250,000 times a week—and a desire to put all those blocked pitches to good use. Artists are selected by a team of curators to have their work displayed, and the roster is rotated every two weeks. An interesting twist to the project is that the artists themselves can target sites with their artwork—it'll be up to you to decide why there are photographs of unicorns wearing party hats during your daily reading of the New York Times. Add-Art won't be too tempting to those who ad-block to streamline for speed or memory use, but for those tired of seeing "ONE WEIGHT LOSS RULE" and the like might just enjoy the web a bit more. Add-Art is free, works wherever Firefox does.