Alias - really underrated, awesome producer, I think he's associated with anticon but he makes some damn fine instrumental albums on his own, especially his latest Resurgam
Blockhead - Already mentioned, seems to get better with each release - I love Uncle Tony's Coloring Book, though Music by Cavelight and Downtown Science are good too. He produces a lot of Aesop Rock's stuff and probably deserves most of the credit for his success.
DJ Krush - he can be hit or miss especially since he's released a ton of stuff over the years, but overall I like his production style. Most all of his albums feature guest vocalists on some/all of the tracks - meiso and milight are decent, recently I've be listening to stepping stones which is split into two discs ("lyricism" and "soundscapes"), both of which are pretty good.
Madlib - Madlib is the man, I like Beat Konducta 1/2 almost as much as donuts, 3/4 (in India) was a bit meh only cuz Oh No made the same album in Oxperiment (only better), and 5/6 is a tribute to dilla and pretty good.
Dabrye - already mentioned, one/three and instrmntl are both great.
Nightmares on Wax - Still love smoker's delight and carboot soul!
The Herbaliser - good funk/hiphop/soundtrack type music, although most of their albums feature guest MCs on about 1/2 the tracks.
Also track down some of the instrumentals of DJ Premier & Pete Rock productions, those guys are pretty much hiphop legends in beatmaking