I recall using an add-on for turbogears called tgws a few years back but I don't know if it works with the latest turbogears. It was pretty easy to build out web services, but I am not sure it has any demo interfaces. It was even easy to add extra services (like xmlrpc).
Sorry this isn't more helpful but I figured it might give you a place to start. As well, for all I know turbogears 2 or django have stronger support for exposing web services out of the box... (haven't done work on that side for a while).