I suppose this should be in usage and support but I'll say how anyways.
You have to have their IP addresses set up, just as you did in OS 9 (except this would be in networking preferences). You can turn on appletalk if you like but I'm not sure if its worth it.
Now in the finder pick go and then connect to server. Type in the IP of the other computer and you get the same login box you got in OS 9. Enter username and password (the username of the account on the other OS X box is a good start) and click ok and you can choose which volumes you want to get on your desktop. From there its just like OS 9 as the disk will show up on your desktop.
Its as easy or easier than it was in OS 9.