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 - ?

    G - Rangefinder mount with autofocus

Generic:

    M42 - First used in Zeiss Contax S (1949) and then adopted by many

          other manufacturers due to patent-less nature.

    T2 - Introduced by Tamron in 1957, with adaptors for virtually all other

         mounts (due to large flange distance).  Used in astronomical

         devices and some mirror lenses.

    C - Intended for cinematographic lenses on very different viewframe sizes

        (often smaller that µFT), it can be adapted to most mirrorless systems.

        It has a very short flange distance, but due to the small radius of

        most C mount lenses, the adapter can be realised as a ring around the

        lens.  In photography, most C mount lenses must be considered fun

        lenses.

Leica:

    M - Classical Leica rangefinder mount

    R - SLR mount, discontinued since 2009

    S - Medium-format mount

Hasselblad:

    H - Current medium format mount of this brand

Minolta:

    MC - Older Minolta mount for manual lenses

    MD - Newer version of MC with aperture information to the camera

    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

Samsung:

    NX - mirrorless APS-C mount introduced in 2010

    NX mini - mirrorless 1" mount introduced in 2014

Voigtländer:

    DKL - the "Deckel" mount used in the Bessamatic