• Their is an application called users and groups in ubuntu which have a really simple and easy to use interface.With this application you could  add/delete/manage groups with relative ease. Go to system-->administration-->Users and Groups             

                           Or you could use the command line option given below

• Go to applications-->accessories-->terminal and type the following

                                 sudo userdel <username>

• This will however not delete the Home directory. To delete the Home directory just use this:

               sudo rm -r /home/<username>/

Content Courtesy: http://www.ubuntuguide.org
Content License:http://www.gnu.org/copyleft/fdl.htm