Introduction to Virtualization - 103 How to Install and Use Sun Virtual Box

There are many good articles on how to use Virtual Box.

Included below are some links.  Let some others use their own words.
Some have Screenshots, some without

the main sites - you can get virtual box from either.  you can get good tutorial info from either.
http://www.sun.com/software/products/virtualbox/get.jsp
http://www.virtualbox.org/
http://dlc-cdn-rd.sun.com/c1/virtualbox/3.1.4/UserManual.pdf

A nice tutorial on how to get Sun Virtual box running on  Windows - this is the older Innotek version, but looks much like it today.
http://www.rasyid.net/2007/05/04/step-by-step-installing-virtualbox-in-w...

A nice tutorial on how to get Sun Virtual box running on Ubuntu
http://www.howtoforge.com/installing-virtualbox-3.0-on-an-ubuntu-9.04-de...

A nice tutoral on how to get Guest Addons to work which will make your mouse work better in the guest machine.
http://www.dedoimedo.com/computers/virtualbox-guest-addons.html

Here someone is installing windows in a virtual box - with screenshots
http://klikit.pbworks.com/How-to-install-Windows-in-VirtualBox

Here someone is installing Ubuntu in a virtual box - with screenshots
http://www.psychocats.net/ubuntu/virtualbox

Here is someone's nice list of things of more things to do, networking options etc.
http://searchservervirtualization.techtarget.com/generic/0,295582,sid94_...

some more HOW Tos at the offical location.
http://www.virtualbox.org/wiki/User_HOWTOS