Starting with the 1E MM2/DSG/WSG on (including PHB/DMG/MM1 reprints), the font used for the "Advanced Dungeons & Dragons" logo was Friz Quadrata Bold. If memory serves, the font used for the book name and much (if not all?) of the remaining text on the 1E hardback covers was Korinna.
For the original 2E hardback books, the cover font was exclusively Friz Quadrata. For the "Players Option" line and the "black cover" reprints of the 2E PHB/DMG/MM, the logo continued in Friz Quadrata but the book title changed font; I don't recall positively identifying it myself [EDIT - and I don't see an entry for it at the Font FAQ].
The high-quality originals are, of course, available for purchase, but lower-quality free/shareware duplicates of these fonts take various names.