Since the rise of digital cameras, film is not always needed.

Types of Film stock

8mm

Amateur film gauge introduced by Eastman Kodak. In the camera, it was the same size with standard 16mm film but with double perforations. At the picture area of a typical 16mm film, four frames of 8mm were recorded, two in the first run and two when turning the film cassette to the other side to expose the other half width, much like audio cassettes are used. When processed, it was slit lengthwise to produce a double length (usually 50ft) Regular 8mm film for projection. A better variant, Super 8mm was introduced by Eastman Kodak in 1965. This had smaller perforations which allowed for 50% increase of the image size and hence more detail could be recorded. The larger frame also allowed for larger projection sizes than were possible with standard 8mm (called Regular 8mm) film. See also respective sections in Wikipedia and Kodak's web site.

16mm

Super 16mm

Super 16mm film is physically 16mm wide, however, when compared to standard 16mm film one will notice that 16mm has perforations on both edges of the film, whereas super 16mm only has perforations on one side. This allows for a wider frame on the film and provides greater resolution to that achievable with standard 16mm film stock.

35mm

35mm Film Stock is regarded as the industry standard when it comes to professional productions. There are a few different types of 35mm film, including:

Two perf
Three perf
Four perf
Super 35mm

65/70mm

This type of film stock is the largest format made, it is generally used for IMAX productions. It is the highest quality film available.

Buying Film stock

Kodak

You can purchase Filmstock directly from Kodak by calling them. Information is at http://www.kodak.com

Fuji

Consider using cheaper Short end and Re-can stocks.

Storing Filmstock

Shameless Plug for Kodak... http://www.kodak.com/global/en/service/tib/tib5202.shtml