I'm sure you can think of more ideas as to how to use AboutTh.is, which will let you put your voice on top of anybody else's webpage. Here's what I've come up with so far; please feel free to add your thoughts below:
Bloggers, email newsletter publishers, and other online business owners typically send their audience to pages which are not under their direct control, such as news articles on which they are commenting. Now, they'll be able to send people to a web address with their own voice and personality, and when those people pass the link around to their friends, it will allow them to subscribe to the original blogger's mailing list.
I actually started thinking about this project when I was trying to help people learn conversational English. People will be able to use AboutTh.is to read an article aloud in its original language, or even translate the written article aloud into a different language.
A lot of people earn income with affiliate programs, which of course involves sending visitors to a landing page owned by the advertiser. Now one can provide a smoother transition to that page, by providing some encouraging commentary that helps the visitor understand the benefits of the advertiser's offer.
Some websites can be pretty confusing, so a little bit of audio instruction can help clarify how to use them. Rather than forcing people to flip between a how-to page and the site itself, everything can appear all on the same screen.
Maybe there'd be a way to personalize online greeting cards? My parents like to send cards using Jacquie Lawson's e-card collection, and perhaps there'd be some way of tying AboutTh.is into that. Although, the more I think about it, the more it'd make sense for the card provider to integrate audio directly into their service.
[Added 11/30] Product and business reviews will come across more authentically when people leave them verbally. AboutTh.is could actually be integrated rather easily into review sites like Yelp and Angie's List, so people could supplement their written reviews with audio versions.