BMW:

BMW Archive VIN Decoder – Much more than a VIN decoder, this site can give you the original paint colour, interior trim, assembly date and all of the factory installed options for your BMW. Database claims to go back to 1928.

RealOEM.com – Not a full VIN decoder, but this site can tell you the platform, body style, model, assembly date, engine and transmission of your BMW with only the last seven digits of the VIN. Very good site for looking up parts as well. Go to the archive section for older cars.

BMW E3 Serial Numbers – A page with full serial number ranges for the 1968 to 1977 E3 platform BMW sedans such as the Bavaria. These numbers are often not decodable in standard BMW serial number databases such as RealOEM.

Porsche:

Porsche 912 & 912E VIN Table – As the first generation 912’s do not have a decodable serial number this table can help you determine the model year or production date of your 912. From the Porsche 912 Registry.

Porsche Option Decoder – Not a VIN decoder but a decoder for the three digit option codes found on the option code decal on your Porsche. This would be on the underside of the hood on the 911 and at the rear of the storage compartment in the 924, 944 and 928.