Bullet Cameras:

A great way to get a camera up in a hurry is to go with a bullet camera. Most come complete with lens and some are weatherproof. Also look to see if it has built in infrared illuminators to help you see in the dark.

Covert Cameras:
Need to hide a camera? this is the way to go. A covert camera can either be disguised or small to not draw attraction. Covert cameras can come in a variety of way, as a smoke detector, thermostat, motion detector, clock, etc.

Dome Cameras:
Useful for its vision range from a ceiling or a mount. Different types of Dome Cameras include: Pan Tilt Zoom (PTZ), or with a fixed or a varifocal lens. Varifocal Lenses allow you to change your field of view. PTZ cameras require a controller.

Network Cameras:

A security camera that resides on an IP address on your network. Very flexible for the purpose of remote viewing.
 

Standard (Box) Cameras:

An industry staple for years. Box cameras are known for their excellent quality and longevity. Most are 24VAC and require a power supply and a lens.

Megapixel Cameras:

Relatively new to the CCTV market. Great for applications that require very high resolution pictures. But they also require a strong computer to run..