Here's a list of voice commands:
CALL / DIAL
Say call or dial then say the name of a contact to call them. If they have more than one phone number you can follow this with HOME or MOBILE for example.
Say call or dial then speak a phone number to call the number.
PLAY / PLAY MUSIC
Starts music playing in the iPod app. Say PAUSE or PAUSE MUSIC, NEXT SONG or PREVIOUS SONG, SHUFFLE to control play.
Say play then say ALBUM, ARTIST or PLAYLIST and the name to play the specific selection.