MacDevCenter.com: File sharing with Windows from Mac OS X::

sudo pico /etc/smb.conf. If you're prompted for your user password, enter it. ...
In this case, we're just going to call it 'shared'. Give yourself some space after the [homes] section by moving the cursor below it and pressing the enter key a few times. Now type in exactly what appears below:


[shared]
comment = Shared Directory
path = /Users/Shared
read only = no
browseable = yes
create mode = 755


And voila -- I've got central one spot on my home network for all my iTunes files. Yay.