It was very easy to use Apache CXF to develop a client for a SOAP web service. All I had to do was call wsdl2java and all the required classes were present. Is there such a client for lisp? If not, what can I do to write a soap client for lisp? The only restriction is that I don't have access to commercial implementations such as franz/lispworks or macs.
There's CL-SOAP which I tried earlier this year. The nice thing about it is that it can read a WSDL file and use that to generate the client proxy. I couldn't get it to work against my SOAP service, and gave up that attempt at some point (I used SBCL). CL-SOAP itself feels a little abandoned, with the last update dated 2005. It might work for you out of the box. If not, the code is straightforward and may do what you need with some modification.
CL-XML is said to have a "SOAP module", which I didn't try out.
The question appears to be asked periodically on comp.lang.lisp, with more-or-less similar answers. You may find more pointers there.
Allegro Common Lisp has both a SOAP server and a SOAP client. I've used both with success, and they're currently maintained and supported (unlike CL-SOAP).
My SOAP server easily handles a few hundred requests a second (from both Java and .NET clients), so I'm happy with the performance.