Does anyone know what sort of chip I need to translate the millivolt signal from a thermocouple like the one found at Ultimachine, to the RAMPS board?

You could use either of these...

AD595( I think this is what ultimaker uses) [www.digikey.com] -----the AQ version is accurate enough.

or AD8495 is the new version but only available in SMT surfacemount and would need a firmware tweak.

I prefer the MAX31855 series. They give you an SPI interface.

I ended up ordering the kit from Makerbot... I don't have time to get it wrong

This AD595 with the thermocouple is working great... until I try to run the E0 motor. I can read accurate temperatures when extruding by hand, but not with the motor. I think it must be in Marlin somewhere... if it were electronic connections, I wouldn't think I'd get good readings at all.

Any ideas?

It is really fussy that ad595. Mine gave me so many problems in the beginning. Stray voltage, and RF were constant headaches. Weirdest part was the stainless shielding would somehow affect readings if it touches the machine frame. Ended up cutting the thermocouple wire at 2 inches and running ordiinary wire to the thermocouple chip. Problem solved.

ha! well, I moved on. I ended up going back to the regular old thermistor. The extra range of temperature readings just isn't worth it. In fact, I really doubt that higher temperatures are the future of 3d printing. I'm betting it goes the other way - lower temperatures, with resins like Stratasys uses.

I am getting a stand alone temperature controller today with a dry relay for the hot end. I really like how I can get high speeds out of the polycarbonate and .05mm layer heights. It is the easiest to control plastic I have used yet and has a high temp range so even with the crazy thermocouple readings I was able to print with it,.

Lets see about the stand alone controller results this evening.