Like many of the above, I mix and match - my MO since getting back into the DM chair has been to grab very old published stuff that most of my players have never seen (only two members of my group are old enough D&D gamers to remember the original AD&D mods, and the only Basic/Expert mods they remember are B1, B2, and X1, so I'f got a lot of wiggle room) and then gut it so it fits my game.
Example: used an old Dragon mag module from the early 80's (Forest of Doom for those playing the home game) that was full of drow, quaggoth, drow, goblins, spiders, orcs, and more drow. I dumped the drow, replaced them with githyank, kept the drow leadership as elves (as befit the campaign world), made all the humanoids goblins of varying sizes, and replaced every mention of a monster with an appropriate flesh-golemy construct mechanically built on the old Psionics Handbook's Astral Constructs. By the time I was done, about the only thing that remained intact was the map and the basic set up (storming the tree fortress).