Forget all that and let Apple's Address Book take care of it for you.
First, create a new Smart Group. I went through my list of contacts and identified the lucky few who will receive cards from me this year (jealous?). In the note field of each, I added the keyword "holiday."
Next, I selected "New smart group..." from the File menu and set the criteria to be "Note contains 'holiday'." Next, I named the Smart Group "Holiday" and presto! My list was complete. In the future, I can add new contacts to the list by simply typing "holiday" in their notes field.
Now to print. Address Book prints directly to standard Avery labels. With your new Smart Group selected, simply select "Print." The print dialog box appears. First, set the "Style" menu to "Mailing Labels." Then, click the "Layout" tab and select the labels you're using. Then click print and you're all done!