Use a mail merge.
Outlook uses Word for performing mail merge functions such as Form Letters,
mailing labels, envelopes, and fax or email merges. For an overview of these
functions take a look here:
http://www.slipstick.com/contacts/printlabel.htm
http://www.outlook-tips.net/howto/mailmerge.htm
http://office.microsoft.com/en-us/assistance/HA011186361033.aspx