Being in a PAL land now (Australia) I'm suddenly aware of a need for a definitive solution for converting RGB to SCART for blissfully clear gaming love. Here then is how I did it:

First I hacked up my custom made SCART extension cable - it had a female SCART on one end and a male SCART on the other end. It was a straight-through cable, each pin went from 1 to 1, 2 to 2 etc. Nothing special. You can use a male ↔ male cable if you like, they're pretty common. Replace one end with a female connector and wire it up as follows:

• Some displays, especially those with TV tuners, require composite video, and won't function with composite sync instead. This is the exception, not the rule.
• Many displays will not enter RGB mode without a blanking signal.
• I used +5v for blanking, but you may need to use a 100Ohm resistor on this line.
• Ground is Ground, you don't have to use separate wires from end to end. One ground line is enough, but you must connect ALL the ground pins to each other on each end.

• RGB-21 Connector in more detail
• SCART connector
• If you're connecting your display to a console or device that doesn't offer a blanking (power) signal, you can easily Add power to your SCART/RGB cable