I posted my first Android app to the market just today.
It is (more or less) the union of Voice Dialer and iPhone Voice Control, with a few other nice command grammars thrown in.
It works nicely except not on HTC Hero.
"Schedule an event for January 12th at 3:20 in the afternoon" is much faster than the manual steps.
"Call Ed Simpson in 4 hours" creates a scheduled event with subject "Call Ed Simpson" and with his phone numbers as click-to-call entries in the even description.
"Play songs by the Beatles"
"Shuffle play songs from Abbey Road"
"What does a cow say?"
It also adds a help panel to detail the fairly rich options for specifying event times, and a settings panel that lets you (for instance) express a confidence in a recognition result sufficient to proceed without confirmation. Some of the grammars are disabled by default, but will work when turned on in settings, provided you have few enough contacts and songs for the speech recognizer to load up all their names.
I'd be keen on any feedback at all, and truly need an HTC Hero user who would run diagnostic builds.