EmailsToThings is an open source Mac OSX Apple script and helper application for converting Outlook and Mail.app's messages to Things' tasks. When using conversation mode, if you click on a conversation, it most of the time selects the latest message, but in some of my tests it selects a random message in that conversation.
Mia for Gmail (was Notifier Pro for Gmail) is a desktop Gmail client which sits politely in your menu bar.
