Ubuntu Unleashed 2011 Edition: Covering 10.10 and 11.04 (6th Edition)

http://www.ximian.com/ The home of Ximian Evolution, the standard email client for Ubuntu.

http://www.mozilla.org/ The home page for Mozilla Firefox, Thunderbird, and the Mozilla Suite.

http://www.spreadfirefox.com/ The Firefox advocacy home page is useful for converting those Internet Explorer types.