Azayzel, you might like Christopher Stasheff's Warlock In Spite of Himself
and sequels. Also, try C. Dale Brittain's A Bad Spell in Yurt
etc., and possibly Patricia Wrede's "... with Dragons" books, T.H. White's Mistress Masham's Repose
and (for a switch to SF) James White's "Sector General" books (medical mystery humor SF -- that enough combinations for you?) I think you also might like City of Baraboo
, Elaphant Song
, and Circus World
by Barry B. Longyear, which are just recently back in print. I'm sure you've already read Douglas Adams.
And obviously, if you haven't yet read Good Omens
by Neil Gaiman & Terry Prachett, run, do not walk, to your nearest bookstore (or internet connection) and get yourself a copy. Possibly more than one.