The Null Device
Another online speech synthesizer demo; this one (ScanSoft's rVoice), however, has multiple accents, including British (i.e., RP), Scottish, Australian (only in sheila, though, and not bloke), Spanish, and not only American but also Valley Girl (more formally known as "Southern California").
Which is rather nifty; it's good to be able to get synthesized speech that doesn't sound either generic-American or (occasionally) RP-British (which some call the BBC accent, except for the fact that nobody on the BBC talks like that these days).
Apparently one of their markets is call centres and voice-response systems (and some of the voices have normal and call-centre modes of diction). Which could explain the presence of a Scottish accent; apparently, studies in Britain found that Scottish accents are considered the most soothing/least aggravating to call centre callers.