CardFinder is a time-saver script to pop-up the Address Book cards related to a message selected in Mailsmith. Selection is based on originator and main recipient of the message.
[robg adds: At first, I couldn't open this script, as I don't have MailSmith ... but in trying to work around that problem, I discovered another hint -- also published today! Having now looked at it, it looks quite benign, but I haven't tested it to see if it works.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040503195240920