Sharing your iTunes collection
The following assumes you want to keep all your iTunes music and movies on a shared folder and ensure new music is always stored there, and that you want to share the iTunes library among multiple users
First, you need to consolidate your iTunes Library to a folder you have chosen (let's say External > Media).
Select the command consolidate library from the File Menu > Library > Consolidate Library (or from the Advanced Menu in iTunes 7). This will copy all your iTunes media to the shared folder and link the iTunes library file to it
The files will now be in the folder while the library file (the index as it were) will still be in the Users > Me > Music folder of your mac.
Copy it to shared Media folder, start iTunes with the alt key pressed and you will have the option to select the library file now on the shared drive
Select the library file you just copied and now both your music and the library are on the external
Press the alt key in any other accounts to get iTunes to see the library file, now both users are using the same index. Make sure both Users itunes have the same location for the music folder set in their advanced preferences.
Also make sure that all users have read and write privileges for the folder and the library file
