The Home Sharing feature in iTunes 9 lets you share music between
computers right within iTunes, but it has a bunch of limitations. Both
machines need to be on one network, and the only automatic transfers
are new iTunes Store purchases--regular old CD rips and non-iTunes
downloads can be dragged manually from one computer to another.
iTunes 9 also added the Automatically Add To iTunes folder to your
iTunes Media folder. Any iTunes-compatible file dropped in here is,
like the sign says, automatically added to your iTunes library. Just
drop it in there and poof, it’s gone. But check in iTunes. It’s there.