Clicking on a field header within the Contacts app on your Mac gives you all sorts of handy-dandy things you can do. For example, if you click where it says "mobile" or home" (or whatever) in front of a phone number…
…here are the choices it'll give you:
The options depend a bit on what applications you have installed, as you can see.
Here's what you get when you click the header next to an email address instead:
I especially like the Send My Card one, as it's a simple way to share your info with other people.
In my opinion, though, the most useful choices come when you click the header next to a physical address:
Map this Address is awesome! What that'll do is open your default browser and take you to the Google Maps page for that address, from which you can get directions and so on. That's much faster than copying and pasting!
Also under that physical address menu are Copy Mailing Label and Copy Map URL. I use Copy Mailing Label when I need to share a contact's address through email, but I don't want to send his entire card to my recipient.
Similarly, you can use Copy Map URL to paste a link to the location's Google Maps page instead.
This really is just the tip of the iceberg, though, for everything you can do with those Contacts headers. Do you guys have a favorite use for this feature? If so, I'd love to hear about it in the comments!