If you open up someone’s contact card in AddressBook, click on the “work” or “home” label next to the address. Then choose “Map this Address” in the menu that pops up.

That’s it! It will open up Google Maps with the address pinpointed.

If you use Outlook on a PC, you can pull up a map (msn.com) using these steps (courtesy of Microsoft’s support site):

To display a map for a selected contact’s address:
Click Contacts on either the Outlook Bar or in the folder list.
Click the contact whose address you want to locate.
On the File menu, point to Open, and then click Selected Items.
Under the Address button, click the arrow, and then click the type of address you want to find on a map, for example, Business, Home, or Other.
On the Actions menu, click Display Map of Address.