Anyone know how to add stuff to the Right click menus of the desktop and explorer?

Ie: select a file, and right click on it and you have the following options...

OPEN WITH
SCAN WITH NORTON ANTIVIRUS
ADD TO ZIP
ADD TO <<FILENAME>>.ZIP
SEND TO >
----
CUT
COPY
----
CREATE SHORTCUT
DELETE
RENAME
----
PROPERTIES

How do I go about adding to this menu?


Eiredrake