A family of Microsoft word processing software products for creating web, email, and print documents.
If the names and addresses are stored in a proper format (a word table with a separate column for each part of the names and addresses; or an Excel worksheet similarly laid out; or a database table), then use the mail merge feature as described at http://www.gmayor.com/merge_labels_with_word_2007.htm.
If the names and addresses are just typed line-by-line in a document, first you'll have to rearrange them into a proper format as described at http://www.gmayor.com/convert_labels_into_mail_merge.htm.