I've modified Masks of Nyarlathotep for
CoC in a dark-horror D&D campaign, as well as various
1e and
2e Ars Magica adventures ("The Well of St. Alban," _Trial by Fire_, _South of the Sun_, and _The Broken Covenant of Calebais" immediately spring to mind).
Several Thieves Guild adventures are quite good, especially in urban environments. To round out my version of Greyhawk City, I've used materials from Warhammer
FRP's city-oriented adventures/sourcebooks, along with Chaosium's Sanctuary, TSR's Lankhmar, Midkemia's Cities and Carse, Haven, etc.