The Raspberry Pi project includes a small number of digital camera modules which are okay for most applications however, they do have their limitations and Arducam have developed a couple of products to overcome some of these limitations such as improved image quality, higher resolution and in some cases lower cost.
16MP Autofocus Camera Module For Raspberry Pi
Arducam 1MP Quadrascopic Monochrome Camera Bundle Kit For RPi
1MP Stereoscopic Camera Bundle Kit