How do I transfer files between one Ubuntu box and another?
Install an ssh server on one box, and then use nautilus (the file manager) to drag and drop files.
Decide which box will be client and which will be server .
Go to the server and install ssh
$ sudo apt-get install ssh
Now use ifconfig to find out the network address of the server.
On the client select Connect to Server on the Places menu.
Use SSH as the service type, and put in the server's ip address you found above, then press Connect
You'll be asked for a username and password for the server.
And you're done.
You should now have a nautilus window open showing the files on the first machine.
 It doesn't actually matter. You can connect to a server from any box in the world.
And if you like, you can set up both boxes as servers.