What a challenge!  For other readers if not for you Sean....

1    Start in the Contacts Folder.
2.    Use a view that will group your Contacts By Category. The view is
called By Category.
3    Select the Category of Contacts to merge. "Select" means make them
highlighted.  You can do that in many ways     and at this stage I will
assume you know how to select items.  But come back and ask if you don't
know how to select more than 1 thing at a time.
4.    To email everyone in that Category, grab the Category heading (it will
be a bar across the screen with the name of your Category group in it) with
your left mouse button and drop it on your Inbox Folder. Release.
4a) Say Yes to the stupid message that creating a new item from these x
Items may take some time.
5.    The names of Contacts in that Category are now in the To... field of a
new email.
6.    Complete the content and click the send button.

Explanations:

Item means an Outlook "thing" it could be any type of thing eg an
appointment, email, task, contact, note.

Navigation Pane - the left side  strip of the screen in Outlook 2002, 2003
and 2007.

Views are way of seeing the content of a folder.  You can change views many
ways. In 2007, the Navigation Pain has radio buttons to change views.

Options:

1    if you don't want people in the To... field, once they are there,
highlight them all (select them) and drag them to the BCC field. If the BCC
field is not showing (in version 2007) the setting is on the Options Tab of
the ribbon at top of screen.

2. If you want to email merge to this category of Contacts it's a little
more complicated.  Let me know if you want to know how.

Regards

Judy Gleeson
MVP Outlook
Trainer and Consultant   www.pragmatix.com.au
My suggested settings for Outlook 2003 are FREE on my website.

.

Outlook 2007 moved New message to contact to the Create menu - so right
click, Create, New message to contact.

Doesn't anyone explore menus anymore?