Sharing Files between Ubuntu machines (even Windows) is super simple.

1. Right click any folder you want to share and select Sharing Options
2. Select Share this Folder
3. If you are prompted with 'Sharing service is not installed' select Install service
4. Authenticate with your password
5. When prompted Restart your session
   

It's that easy! Now you can share files between other computers on the network!

To access files on other computers go to:

Places>Network

and choose the computer you want to access!