Google the Radio!
I don't think that there is a big future, at least in the next five
years for speech on the desktop. Speech recognition still takes too much
computing power and is still too inaccurate to be viable replacement
for the keyboard. I think that the next big area for speech recognition
is indexing audio streams (think NPR, and CNN) for search engines.
Our colleages over at HP's research lab put together SpeechBot , a prototype system that allows you to search a number of audio streams. It uses Sphinx as its speech recognizer.
StreamSage is building a business around indexing audio streams for search. They have a demonstration of their technology at CampaignSearch.com.
There's a good overview of the field in a ZD Net article: Search engines try to find their sound