You may be interested in BeeLine Reader [1]. It puts a color gradient on alternating lines to text to hopefully let you read faster. I think it works a little bit. When I really want to read an entire article but don't want to invest too much time, especially if it's somewhat fluffy, I'll use Spritzlet set to 700 wpm [2].
Interestingly, when people see BeeLine Reader for the first time, many of them think (incorrectly) that it's a sentence-based algorithm instead of a line-based algorithm. Their belief often persists even after being told (by me, the creator) that it is in fact line-based. We've thought about doing something that's sentence-based, or syntactically or semantically aware, but as others have pointed out those tasks are much more complex.
1: http://www.beelinereader.com/
2: http://www.spritzlet.com/