Speech recognition software's getting better all the time. I've tried out IBM's ViaVoice on a couple of Macs and been impressed by the results.
The program has to "learn" the user's voice pattern, and the more time spent "coaching" it the better the end result, but it does allow you to blather away to the machine and see the results as text, complete with proper capitalisation, punctuation and formatting.
For meself I still prefer to type (particularly as colleagues could be puzzled if I start ranting at the screen when posting here!), and I don't think any program is yet able to write HTML - which means that even a post written by a speech-recognition program would need to be tweaked and formatted with the line-breaks and other odds and sods.
But if your not a natural with the tripewriter, then ViaVoice (or its rival, Dragon Dictate) would seem a pretty good alternative.