Vimeo_thumbs is a project mainly written in PHP, it's free.
Get Vimeo thumbnail URLs
Prints the URLs for various sizes of Vimeo thumbnails.
Usage:
./vimeo_thumbs.php
Example: $ ./vimeo_thumbs.php http://vimeo.com/17111307 small: http://b.vimeocdn.com/ts/105/825/105825531_100.jpg medium: http://b.vimeocdn.com/ts/105/825/105825531_200.jpg large: http://b.vimeocdn.com/ts/105/825/105825531_640.jpg