To share your songs on a network... you need two computers here, one a server and one the client. The server holds ALL music. The server must always be running, too. So, here goes.
On the server:
1. In the Shared (Macintosh HD->Users->Shared) folder, make a folder named "Network iTunes Library"
2. Tell iTunes that that is your new library folder. Preferences, under the Advanced tab.
3. If you need to, move your music across to the new Library. Make sure that you have placed the original songs in the library, and not aliases. This means that you need to check the "Copy Music into iTunes Library" check under the Advanced tab in Preferences. After all your music is in the Library, go on to the client section.
Once you have the server running with all your music, do this on the client:
1. Open iTunes.
2. Go to Preferences, then Advanced
3. Make sure the "Copy Music into iTunes library" checkbox is checked.
4. Choose a new default location for the iTunes library. When that little window pops up, navigate to your Network. Choose the server, and connect to it. You can mount a network share through an "Open..." dialog box or you can connect to the server in the Finder and then just follow that network share in the Open dialog box. You will need to mount the "Macintosh HD" network share. And that requires a valid password to the server. Assuming you do... open the Shared folder on the server and then select the "Network iTunes Library" folder.
5. You should be good to go!
[EDIT] Read the rest of the the thread to see what some people thing is wrong... how dare they....
It might be worth your time to do so, to save many hours of work for naught.
I have not actually tried doing the above, but I think it would work. You just need to repeat the client instructions for each client. If you have a computer that is always on and not asleep, use that computer as the server. Or, if you have a spare Xserve laying around the house like
5300cs does you can use that...