So you want to improve your knowledge of Unix but you don't have access to a Unix system. Never fear, the very nice people at www.arbornet.org provide free Shell Accounts. It only takes about 5 minutes to get logged in and set up.
Follow my article "Practice your Unix skills with a free shell account", in the Basic Unix Commands section or click here. This should get you up and running in about 5 minutes. Enjoy.