Remote Speech
This is a great way to pull a prank on an unsuspecting Mac user. Note: This is an experimental feature. It might work for you, or it might not. Don't get angry; it will work in the next version.
Remote Speech operates by sending Apple events to other computers on your local (or perhaps non-local) network. Therefore, you must speak Mac-to-Mac, and there are many things that can go wrong.
To begin, you need to set up the remote computers you want to speak to.
On the remote Mac, go to System Preferences :: Sharing.
Enable (check) Remote Apple Events, and, if you are using Leopard, select Allow Access for All users.
Near the top of the Sharing pane, there is a description line similar to the one pictured below. Note the address ending in .local
Or, go to :: About This Mac :: More Info :: Network, and note the IPv4 Address.
Now go back to Verbalize on your computer. Click Remote or press ⌘-R to open the Remote Options panel. Check the Speak Remotely box to enable the feature, and enter the .local or IP address of the remote computer you noted above. If you want, you can tell Verbalize to change the volume of the remote computer before speaking.
At this point, anything you speak with Verbalize will be spoken on the other computer instead of yours. You can toggle the Speak Remotely checkbox any time to switch where the speech is sent.