I don't know if this has been posted yet -- apologies if it has.

Dragon, who publishes Naturally Speaking, has a free app for Blackberries that allows you to dictate email (there appears to be a similar product for iPhones). It works by communicating with Dragon's speech recognition servers. I haven't played with it much yet, but on my Blackberry Storm, it's very fast and extremely accurate. I was able to dictate in a natural manner, speaking quickly and not pausing between words.

The only downside is that, unless you have an unlimited data plan, you might incur some additional airtime fees. Presumably, you might have some privacy concerns, as the message content is communicated to Dragon's central server for recognition processing.

I like this app a lot -- I am, literally, all thumbs when it comes to entering text on my Blackberry. This way, I get fast and accurate content. You can see it here:

http://www.dragonmobileapps.com/