This socket is rated at 32VAC 15A or 110VDC 15A. It was designed for 32 volt use for farms but this plug has found its way into caravans & motor homes for 12 VDC supply.
This is used for 230/240 VAC 10A supply
Not too common but this is designed for 110VAC 10A supply, the welding equipment manufacturer CIG (now BOC) use these for a 77 volt supply for some welder ancillaries on older machines.
This is used for a 240V 15A supply; the earth pin (the bottom one) is longer to accept the 15 amp plug
This is used for 230/240 VAC 10A supply for special purposes use i.e. lighting points. Some people also use these for 110 volt supply while others use it for 12 or 24 VDC.
This beastie is rated for 240V 10A, most probably for clock circuits. Not that common, some 240-110 stepdown transformers were fitted with these as NEMA1-15 plugs fit quite nicely.
These are Clipsal brand sockets, more info from
www.clipsal.com (posted for Darren Carroll)