Indeed. There's the world of 35mm cameras, which is what full frame digital SLRs are (think Canon 1D X and 5D III, and Nikon D4 and D800, having a sensor fo 36x24mm). Many digital SLRs have cropped sensors — the Canon 7D, 60D and 600D have a sensor that is 1.6 times smaller than a full frame (22.2x15.8mm). More: http://en.wikipedia.org/wiki/Full-frame_digital_SLR
The next level of cameras is medium format, which are vastly more expensive and have much larger sensors. They're generally used for studio work, where light isn't a problem. They're popular for fashion and product photography.
Then you move up to large format cameras with even larger sensors, although most of these still use film (but digital backs are available, and tend to have hundreds of megapixels). Large format cameras are still popular for landscape photography.
The next level of cameras is medium format, which are vastly more expensive and have much larger sensors. They're generally used for studio work, where light isn't a problem. They're popular for fashion and product photography.
Then you move up to large format cameras with even larger sensors, although most of these still use film (but digital backs are available, and tend to have hundreds of megapixels). Large format cameras are still popular for landscape photography.