The answer by Gumbo is missing an ingredient. An hcard/vcard is required to have a name.
http://microformats.org/wiki/hcard#Property_List
Also the address tag should not be used in this case as it is specifically used to relate to the author of the page it is displayed on.
<div class="vcard">
<span class="fn">Tristan Ginger</span>
<span class="adr">
<span class="street-address">169 University Avenue</span>
<span class="locality">Palo Alto</span>,
<abbr class="region" title="California">CA</abbr>
<span class="postal-code">94301</span>
<span class="country-name">USA</span>
</span>
</div>
Most business wanting to display their address on their website should use the following:
<address class="vcard">
<span class="fn org">Tristan Ginger Inc</span>
<span class="adr">
<span class="street-address">69 University Avenue</span>
<span class="locality">Great Bookham</span>,
<span class="region">Surrey</span>
<span class="postal-code">KT22 9TQ</span>
<span class="country-name">UK</span>
</span>
</address>