With noise cancelling headsets (as suggested by ewwhite), you need make sure they have noise cancellation on the mic as well, otherwise the person in the datacenter will hear fine, but everyone else on the call will have to put up with the ambient noise. I've had that problem before, buying a headset billed as noise cancelling, but with a cheap boom mic that picks up all the ambient noise. So just make sure the mic is a quality mic if you go that route. Unfortunately, the most reliable way I've found to determine that, besides/in addition to reading reviews is looking at the price. Quality mics and speakers are expensive.
The other option I've used with success is to go with a mic-less headset. Basically, they use the speakers in the headphones to pick up vibrations as they go up the bones in your face, do some math to make the appropriate adjustments (for the fact that bone is denser than air and makes thing sound "deeper") and then send it as outbound audio. I've found that these do a good job of filtering out ambient noise by nature of the fact that the ambient noise doesn't vibrate up your facial bones, unless your face is pressed against the noise source.
I have a high quality, expensive pair that's always coupled to my phone, and almost always on my ears (I use it for music when not on a call), so I don't even notice the ambient noise in our server room or datacenters any more, and the people I'm talking to don't know any better either. This is the route I'd recommend, since you can use it for both work and personal uses, while writing it off/getting the company to pay for it as a work expense. YMMV on that last part, I suppose.
