British Telecom has introduced a new text to speech service that allows you to send a text message and have it received as speech on a landline, or even a mobile. To promote the new service, for the first three months, the text to speech voice is none other than the great Tom Baker.
You can get a sampling of the results here, but be warned, The Doctor has quite a potty-mouth and that makes it somewhat NSFW. Also, you'll need Flash.
The idea has been taken a step further here, as The Doctor indulges in a little karaoke.