This AppleScript will search Apple's Mail for all available mailboxes and then ask the user to speak the name of a mailbox. For example, responding "Sent" will activate Mail and make the Sent mailbox visible. Additionally, if you have created local mailbox "Action Items," speaking "Action Items" will take you to that mailbox. If you have account mailboxes, the account name will prepend the mailbox name.
Other script hints on this site can be combined with this script to read the messages, senders, and subjects, if desired.
[robg adds: Due to the length of the script, I uploaded it as a text file to the macosxhints' site. I haven't tested this, beyond insuring that it compiles...]

