People in the know pronounce WSDL "wizdle"

WSDL, which is sometimes pronounced "wizdle," allows a company to sum up the services it's offering and outlines the information needed to invoke that service.

Source

The owner of the web service that my client software connects to wizdle'd me today. I'd not heard it before.

Personally I say W-S-D-L or W-D-S-L pretty much interchangeably.