AppleScript is one of Apple's biggest technology gems -- so much can be done with it, but so few people really understand how powerful it is. Andreas Amann recently updated his Mail Scripts package with several new scripts that are worth checking out if you use Apple's Mail.app.
Mail Scripts consists of nine AppleScripts, seven for Mail.app and two for Apple's Address Book. The package includes Add Addresses (Mail); Archive Messages (Mail); Change SMTP Server (Mail); Create Rule (Mail); Remove Duplicates (Mail); Schedule Delivery (Mail); Send all Drafts (Mail); Export Addresses (Address Book); and Export Addresses (Address Book).
The interface Amann used with the AppleScripts is very easy to navigate and makes sense to the user when launching the scripts. I used most of the scripts over the past couple of days and all worked really well -- getting rid of duplicate messages took over 1000 emails out of my inbox.
You will definitely use some more than others, but it's great to have the option.