Instrumentals is a pretty broad category but i'm assuming you're talkin about DJs.
Kid Koala and Dan the automator (together and separately) have done a lotta collaborations, most of them being successes i.e. deltron 3030 and handsome boy modeling school.
Then there's downtempo music such as Bonobo, Blockhead, Skalpel, Cinematic Orchestra, etc... All do their thing well so if you want to cruise down the mountain with some chill beats...these guys do the job for me anyways.
If you want more hip hop, Jazz influenced (your madlib and co.), go for Prefuse 73 and Amon Tobin. Kinda hard to get into, but if you're a avid listener for sounds so underground it goes overground, try them out. If you want some some songs they made try:
Prefuse 73 - Nuno and End of Biters-International
Amon Tobin- Four Ton Mantis, Verbal, Sordid, and Chocolate Lovely