Safari has a "Reader Mode" which removes everything from a website with an article but the text. Does anyone know of an open source library which provides the same functionality? Or, do you think it would be difficult to implement?
Safari's reader mode is based upon Arc90's Readability(the original, not current, one), which is Apache-licensed. Here's a PHP port of it. Some more searching will probably turn up various other languages. (You didn't really specify where you were asking about implementing.)