A lot of hip-hop producers for sure, on at least two Stone Cold Classics (Nas' "The World Is Yours," above, and De La Soul's "Stakes Is High," discussed here). At least 40 rap songs feature Ahmad Jamal samples, according to a recent Associated Press profile of the pianist; that same article says his website links to these samples. A little digging around revealed an external page which does, in fact, pair the source material with the new creation. The WhoSampled database has a sizable little Ahmad Jamal archive; it's interesting to see just how many producers flipped the same track for different purposes. To channel De La, everything Ahmad Jamal plays could be a hip-hop quotable. [WhoSampled: Ahmad Jamal]
P.S. Ahmad Jamal has new music out, and new old music out. A Quiet Time is the disc from early 2010, recommended from these quarters, and reissue masters Mosaic Records recently put out a box set of his trio recordings from 1956-1962.