Jaime,
Check out http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnfoxgen7/html/vfpws.asp - Walkthrough: Creating Web Services with Visual FoxPro
You can also set up other web services(http://www.xmethods.com) the same way as in the article.
Note: I would use the ASP connector. there's a bug/fix for the isapi connector, but, if you're going to distribute your web service, asp is simpler since it's built in...

>Hi All
>I have to publish a simple ( functionality-wise ) Web Service that has to set some switches in a VFP Database. Is there somewhere an example on how to publish the Web Service, from A to Z? ( meaning also showing what changes to do to the app to be a Com Server, etc... )
>
>Thanks
>Jaime