SET (Secure Electronic Transaction, from SET Secure Electronic Transaction LLC) is also one method of sending credit card information over the Internet securely, using strong encryption.

I can only comment on Finnish side here: Luottokunta (the credit card corporation responsible for VISA and Mastercard in Finland) specifically told people not to send credit card information to the shop over the Internet - instead, they recommended snail mail, phone or fax, which was pretty strange because faxes and telephone lines in general are less secure than PGP or even the 40-bit SSL that was used at that time.

They chose SET for this, but it never caught on - I heard it was pain to implement at server, so only few shops in the end decided to use SET. Furthermore, the SET client was only available for Windows. Currently, Luottokunta approves the use of SSL, too.