I wanted to setup a simple webfinger server for myself today and there was nothing around so I wrote my own - it's really basic:
http://github.com/darron/webfinger-sinatra
Grab it and improve - you can see it in action here:
http://froese.org/.well-known/host-meta
http://webfinger.froese.org/webfinger/darron@froese.org
Grab it, fork it, do whatever you want with it - let me know if there's any questions.