I'm suprised no one has even mentioned J-Dilla: http://en.wikipedia.org/wiki/J_Dilla
and seeing my screen name, you obviously know I'm a huge fan.
For those who don't know him, he's an underground hip-hop producer who essentially started Busta Rhymes career and many others, and, not to mention his great music.
Other great producers who reflect J-Dilla would be: Black Milk, Symbolyc One (SFP is smoooothhh), Madlib so on and so forth.
But, seeing as he did die, and, there was little hype about it, I think that people simply knowing of J-Dilla let alone hearing, is dieing, most underground listeners aren't even aware of J-Dilla, which is a saddening fact contemplating his great music.
Here is some good music by Jay Dee which I hope will give you a good idea of his hyped music production:
Reunion (Produced by both Black Milk and Jay Dee): http://www.youtube.com/watch?v=3qyT4Hxl4ck
Won't Do (His most popular song, although not nearly the best): http://www.youtube.com/watch?v=vVYza0NiWuU
The Official (produced with Madlib, one of the singles off of Champion Sound): http://www.youtube.com/watch?v=kBzoPvOAsuI
FTP (with MF Doom): http://www.youtube.com/watch?v=-B0Oens2HUo&feature=PlayList&p=4A18BD714C5431B7&playnext=1&playnext_from=PL&index=12
I hope that, you hip-hop listeners have a better idea of who J-Dilla is, and, that he is in fact a great producer who has been slept on seriously.