System Preferences -> Universal Access -> Seeing -> Zoom
Two fingers dragged up or down while holding down the control key will zoom the whole screen. If that's what you're seeing, you'll find that in a slightly different place in Mountain Lion than where BobHarris said. It's now in System Preferences -> Accessibility -> Zoom.
If you are having "pinch" gestures zoom in specific zoom-capable apps, you can turn that gesture off in System Preferences -> Trackpad -> Scroll & Zoom.