Possible Duplicate:
Get e-mail addresses from Gmail messages received
In Gmail, you can tag one or more emails with a Label:

I know I can select the label to see the emails in question, but what I want is to get everyone's email address associated with these labels for export. In the above image, I'd want the email addresses of Lifestreams Blog, Ozh, and WordPress since they're tagged 'planetozh'.
EDIT:
Let's assume I can download all the emails into Mozilla Thunderbird and view the emails in an ordered list with the label set correctly (using IMAP). How could I export the list of email addresses (duplicates are not a problem) this way?