Frank Hellwig has a 2.1/3.0 parser and address-book page generator. See his site at vcardphp.sf.net.
Kai Blankenhorn has a 2.1 card generator (not a parser). See his work at www.bitfolge.de/?s=phpvcard.
Flaimo has a vCard generator, too, at flaimo.com/php_scripts.php (scroll down past the iCalendar stuff).
HORDE has a vCard data element in their application framework, but I don't quite see how to use it outside that framework. The doc pages for it are at http://dev.horde.org/api/horde/dev-doxygen/html/classData__vcard.html .
Of course, you can always search for more vCard stuff under PHP, too: http://www.google.com/search?q=vcard+php.