You could read the support files at Unbuntu or download a Linux guide from
www.computeractive.co.uk but because you may need to refer to the guide
often then a book on Ubuntu is best. It will teach some of the most used
commands and the ways Ubuntu works.

Ubuntu Hacks by Kyle Rankin is the one I started with. Amazon.com has a good
list if you just search for Ubuntu there or you can even get them at eBay.