Add Notes to Events, Contacts Created With Data Detectors
When you use Mail in OS X 10.5 and 10.6, you may have noticed Apple's data detector technology at work. Data detectors scan inbound messages for addresses, phone numbers, and dates and times; if you hover over these items in an e-mail message, you'll see a dotted outline and a triangle indicating the existence of a contextual menu. Click the triangle to reveal the menu, and one of the options will be to create a new contact in Address Book, or a new event in iCal, based on what's in the associated bit of text.
Because this feature is fairly well known, you may be familiar with its basic usage already. What you might not know is that it's easy to associate additional text from the e-mail with your new event or contact. Just select the other text first, and then use the data detector menu on the desired address, phone number, or date. When the new event or contact is created, the additional text you had selected will automatically be added to the Notes field in iCal and Address Book.
If you're used to creating events (or contacts) and then going back to add your notes, you'll appreciate the time saved by doing it all in one step.