If you mean interoperate on a network then there are various howtos such as this one, to help you: http://vista.blorge.com/2008/11/02/h...n-one-netwo rk/ If you mean just software, theres OpenOffice, Firefox, VLC media player, The Gimp, and others that run on all three platforms. You could share your itunes music over the network and access it from Linux if you install
Exaile or rhythmbox, ...