Opera, a web browser, offers text reading and speech recognition capability.
The idea of having your browser read some email, an article or book to you - while you did something else, or just to rest your eyes, or if you had a hard time seeing, sounds attractive.
My experience with text to speech software is (a) the voice is annoyingly mechanical (okay for a diversion but not something I could listen to very long) and (b) the interface is clumsy e.g. I have to highlight text or otherwise do something special each time I want to convert text to speech.
There are commercial applications that have a wide selection of voices, allow saving as mp3 files for later listening on a portable device, and that have a more sophisticated user interfaces than the highlighting technique. I've only tried the free versions of some, but nothing grabbed me making me want to purchase the software.
This technology has been around for quite a while, but never seems to really take off, at least for casual users. It may be the equivalent to "books on tape", in that it is useful/desirable to a relatively small segment of people but not the majority of users.
Reading the written word, in a way that is appealing to humans, seems to be a uniquely human characteristic. Maybe someday a computer voice will be able to catch the inflections and feeling, but for now I'd rather have a human read to me than Microsoft Sam.