If you ever developed a webservice in WCF, you probably already know that WCF automatically generates WSDL documents by splitting it in several files according to their namespaces and using imports to link the files. This is all very nice and standards compliant as it should be, the problem is that there are still many tools out there that don't support this. If you ever had to deal with this issue before you probably used Christian Weyer's blog post as a solution to make WCF output single file WSDL documents.
A few days ago I had a similar problem, I didn't want to change the way WCF produces WSDL, but I did want a single file WSDL for documentation purposes. I searched for a tool to do this, but I didn't find any, so I did what a good developer should do, I developed a small tool for this. I'm also making it available under an open source license, so if you ever need it you can find it here: http://wsdlflattener.codeplex.com/