I'd suggest digging around the fringes of the Samba docs. There's a jolly but apparently authoritative guide to cifs, for example, which describes it as 'a recipe for protocol soup'.

Other than that, not much. If you're running on linux there are a couple of modules that wrap around samba libraries. I haven't seen anything that does the same on windows, apart from some modules in the activestate distribution which are only really relevant to interactions with a domain controller (eg Win32::NetAdmin).

Last resort: if you're on nt/2000 you can try reading the output of winfingerprint. or the source...