Stanza is one of the big players in online e-readers, and with good reason. Also, did I mention that it’s FREE? Check them out here: http://www.lexcycle.com/
Stanza will read texts aloud as you follow along–a fantastic tool for reading for the first time or for reinforcing rereading. I love the idea of having this app on on iPad: the iPad is big enough that you can read and follow along, but it’s small enough that you could plug in your headphones and hold the thing in your lap as you listen. I feel like this is exactly the kind of thing that the iPad does well.