How to use microformats to export your contact details
I wrote this post a while back. The content can still be relevant but the information I've linked to may not be available.
Shape Shed has written a nice article explaining how to use the hCard microformat and how to exploit the microformat data with a one-click 'add my details to your address book' link. The example given uses Brian Suda's hCard to vCard transformation. Cool.