These are great recommendations, since I've never heard of the companies before :) I have a friend who recently joined Tempo Automation, who seem to be able to do this too.
Sadly it seems that while in the last year or two many new companies have entered this field yet, I personally haven't had much time to shop around and try anything but Oshpark. Exciting times though!
Oh, you mean PCB milling! Well never mind then; those three are all for metal and plastic milling. I worked at Plethora for a bit, I forget that "milling" means different things to different people.
Sadly it seems that while in the last year or two many new companies have entered this field yet, I personally haven't had much time to shop around and try anything but Oshpark. Exciting times though!