from about.com...
http://rap.about.com/od/toppicks/ss/Top50Producers.htm
10 rick rubin
9 timbaland
8 kanye west
7 the bomb squad
6 marley marl
5 large professor
4 rza
3 dr dre
2 pete rock
1 dj premier
don't know how old this is, pretty solid though, yeah? eric b and lil jon are the glaring omissions for me.
my 10:
swizz beatz, just blaze, the neptunes, j dilla, timbaland, kanye west, the bomb squad, rza, dr dre, premo.