Dave Ligthart

Import users from vcard as subscribers. 
Works with populair websites such as linkedin and gmail.
Notable features:
<ol>
<li>Import users from vcards as subscribers to your website.</li>
<li>Import user contact data from populair websites such as linkedin and gmail.</li>
</ol>

WP-vCard

Import users from vcard file format. Works with populair websites such as linkedin and gmail.

56 Degrees

This plugin enables upload of the vCard files. It adds the *.vcf extension and text/x-vcard MIME type to the list of allowed uploads.

WP-vCard vs Enable vCard Upload