Canon:
    FL - Introduced in 1964
    FD - Another mount (incompatible with FL) feat. automatic aperture
    EF - Another incompatible mount, EF stands for electro-focus
    EF-S - A newer variant of EF with shorter flange depth, allowing
           for manufacturing of less expensive wide-angle lenses. Not useable
           on cameras with crop 1.0 and on EF-only cameras.

Contax:
    N - ?
    Contax/Yashica - ?

Generic:
    M42 - First used in Zeiss Contax S (1949) and then adopted by many
          other manufacturers due to patent-less nature.

Leica:
    R - ? several variants

Minolta:
    MD - Older Minolta mount for manual lenses
    AF - (1985) features autofocus, several generations.

Nikon:
    F - Introduced in 1959
    F AI - (1977) - Added electrical interface for automatic aperture control.
    F AI-S - (1979) - Added a mean to tell camera current focal length.
    F AF - (1986) - Added screwdriver AF coupling, compatible with older mounts

Olympus:
    4/3 System - (2002), the new "digital" mount together with Kodak

Pentax:
    K - the original mount as introduced in 1975
    KF - the world's first autofocus mount, 1981. Abandoned.
    KA - the K mount plus electrical contacts to detect the min/max lens
         aperture and also whether the 'A' aperture mode is enabled.
    KAF - the KA mount plus autofocus
    KAF2 - in addition to KAF features implements power zooming and
           adds MTF information to the lens data