There was a recent item in one of my Digg feeds that covered on-line text-to-speech engines. The next most obvious step, of course, was to incorporate it (the text-to-speech, not Digg) into a jQuery plugin: http://www.outstandingelephant.com/jvozme
The plugin is a standardista's nightmare (iframe, Flash), but it gets the job done in only a couple lines. The site powering it is vozme.com, which looks like the most open of the TTS sites covered in the article (it uses the Festival engine, for example). It seems that the folks at vozme are just providing the TTS as a free and open service, and they actively encourage people to link to their engine, but I would still try to avoid slamming them with requests for pages and pages of speech. It would be easy enough to run a TTS engine on one's own site and have a lot more control over things. More than anything, this is a "because I could" sort of plugin. --Chris