In looking into this following my query last week about creating resource files, I was pointed to ZipStorer which is a single file C# as well as a Codebase project and also the built in (since .NET 3.5) .NET ZipPackage class.
Of these my favorite for C# is ZipStorer (Thank you Brian and Turgit for reminding me of it) and for C there is PhysicsFS (Thanks John Bandela!).
The .NET ZipPackage is interesting but can't apparently understand zip files which lack an XML mime type for each type of resource stored, so I'll leave that for now. My use case is a utility in say C# which bundles up all the resources into a zip file then use PhysicsFS to read it in the C/C++ SDL games. Expect to hear more!
Anyway Happy Holidays or as we British say "Merry Christmas".