I'm definitely not the programmer at our CNC's nor am I the guy capable of knowing a whole lot about RPM and proper cutting speeds. However I do know quite a bit now about stainless steel, steel (heat treated, cold rolled, hot rolled, etc), and 6061 aluminum. We also toy around with some nastier materials like magnesium, titanium, and other random stuff like plastics of all kinds, bronze, brass, and rarely some silver.
I know quite a bit about how you should generally run mild and tool steel or aluminum... however stainless, 17-4 stainless, H13 steel, and B16 are very nasty.