I tried http://www.vrcommander.com/ once.

It's VERY easy to setup. There's a small flash video included that explains you how to set it up.

More information in this thread: keyclone + voice recognition a marriage made in heaven.

Or you can use the search engine to find even more threads on the subject. I think there is a fellow dualboxer who has created his own voice recognition software specificly for world of warcraft. I just can't remember his name or the name of the program.