My project is about to introduce SOAP. It's going to be used for C++ <-> Java and C++ <-> Flex communication. I'm responsible for refactoring our apps to take advantage of Java business rules engine and new Flex gui.
What resources are must read for C++ SOAP? I've read W3 materials. We're probably be using gSOAP on Solaris boxes.
There are some reasonably good books on SOAP, like Programming Web Services with SOAP by Snell, Tidwell, and Kulchenko; I've given that to people to introduce them to SOAP on projects in the past. I don't know of a C++-specific book, but the gSOAP site has pretty decent documentation.
I think the really key thing is probably to not dive into a complicated project right at first; there are some SOAP tutorials around, like this one, that build simple web services using gSOAP. Get the SOAP version of "Hello, world!" going firt, then maybe build that eBay client in the example, and you'll learn a lot of things you'd learn much more slowly and painfully trying to build a big example first.
Another option is to not use SOAP. Have you considered something like Protocol Buffers or Thrift?