[iTunes] multiple libraries on different disks

[henri]

On a macbook with 120G HD, still running Tiger.
I have iTunes folder on a different partition and thought I had 
plenty of room, until I got into podcasts.
I've used the built-in ability to have multiple libraries but that 
doesn't make a new music folder I could put on an external USB drive, 
it does it with the index or something in the one iTunes folder.

I want to have another library or two on different drives. Do I need 
to run multiple copies of iTunes for each location or is there a 
library managing app that would allow me to run one iTunes and access 
multiple libraries on different drives?