I use Teleport all the time and just added a Cinema Display to my Intel Mac Mini, which freed up my Sony 15" to go back as a main screen for my iBook (which has a hack on it to make it video-span rather than mirror). Here's what it looks like all set up;
Teleport allows the bluetooth keyboard and a mighty mouse to control all three screens.
Now here's the unexpected bit - I have the Sony set up in Teleport to be at the bottom right of the main 23" on the Mini - like this;

Then I have my iBook G4 setup like this;

So I can move the mouse to the lower right part of the main screen, which teleports me to the right screen, move down the 15" and then left, which takes me onto the laptop screen. If I'm on the laptop and want to get back to the main screen, I quickly flip the cursor to the right screen and then up to the top left corner of the 15" and it appears back on the 23" (leaving the cursor on the top left corner which I have set to be a 'disable screen saver' hot corner).
Now I don't know about anyone else - but I think that is cool!
{update March '08 - I've now changed the iBook for an MBA - both machines are running 10.5.2 with Teleport 1.0 & it all works perfectly - even with two screens on the laptop - file drag and drop too - brilliant stuff}
Teleport is such a cool app that Apple should {have} paid Julien royalties and bundled it in with Leopard.