The address book widget that comes with OS X Tiger is a great way to find someone's information very quickly.
I find it to be quicker than launching the address book, and looking through all of your contacts.
Here is how to do it:
1. Click on your Address Book widget on your Dashboard.
2. Use the search box on the widget to find an address book entry that you have fully entered the info into. It should have a phone number, street address, and email address.
3. Once you have found someone, you can try a few different option.
5. Click on their Phone #. This will bring it up in onscreen in huge type.
6. Click on their Street address. If you are connected to the internet, it will launch your default web browser and use Mapquest to bring up a map to that specific address.
7. Click on their Email Address. It will launch your email client and have the address already entered.
8. Try it out with other clickable items. For example, if you have their AIM instant messenger info in their entry, clicking on it will launch the chat client.
This is cool stuff, and it makes Address Book so useful.