Andrew,
I have created several web services using as a starting point the excellent soap-gateway package made by William Byrne (thank you William!).

The soap-gateway package makes the creation and publishing of web services very easy, but you'll have to write your own procs to invoke a web service from Aolserver (I could provide a working example).

The soap-gateway package internally uses ns_xml, but I suggest that you use tdom as the preferred xml parser in your tcl scripts.