Iphone: [AppleMac-Intel-PowerPC] syncing program/management of files located under other logons and drives

[AppleMac-Intel-PowerPC] syncing program/management of files located under other logons and drives

I wondered if anyone has suggestions on syncing programs or information on how to
access a "master" Document Folder from 3 different logons.

I have my original iMac logon (admin) and then created a user logon for me to play
around with and get used to the mac. I also created a logon for my hubby to sync his
iPod to. All of the logons are quick switcher and I enabled sharing so when I launch
FINDER I can gain access to the files under the other user logons (I think!) by searching.
Hubby's logon has some music files that I would like to also have access to for syncing
with my iPod. So I dragged them over to my user Music folder. Plus I backed them up on
an external drive. I would like to tidy them up and remove duplicates. If I put ALL the
files on the external drive and then log on and tell iTunes to get music from the one
folder (Add to Library) I can reduce the redundancy.
But I don't always keep the external drive connected (like now, I moved only the iMac to
my dining room table upstairs). So iTunes can't access that main file because the external
drive is not connected. Is there some way to put all the files under one of my logons and
then have the other 2 users logons still have full access?
I have a similiar problem with photos and documents. Sometimes I save or create files
under the admin logon and sometimes under my user logon but I would like to have
only ONE folder that lists all the documents so that either myself or my husband can
access it from our user logons even if it was created when I was on the admin logon (for
example a scanned receipt for our TV set or the pdf owner manual).
Can I somehow link to a main folder of documents located on the iMAcs hard drive form
our various logons? Or do I always need to launch search in Finder and wade through
everything?
If the answer is already on a mac forum somewhere I would appreciate the link. Sandi