Links: Information about playing-cards and tiles
The International Playing-Card Society caters for people interested in all aspects of playing-cards, including collecting, playing, and historical research.
Chinese Leaf Game - an article on the Chinese origin of playing-cards and card games by David Parlett.
Further information related to playing-cards can be found in the International Playing-Card Society FAQ, which includes a section on The Most Frequently Asked Questions About Playing-Cards.
Andy Pollett's Playing-Card Picture Gallery has illustrations on many of the standard regional playing-card patterns used around the world, with much useful historical and general information. There are also sections on early cards and non-standard cards, and some game rules are included.
The Italian site tretre.it included a section on the History of Playing-Cards
Antal Jánoska's site Szerencsés Kártyajárást has information on playing-cards and card games in Hungarian, with German and English versions planned.
The IPCS New Issues pages have a growing collection of reader contributed information about various recently published packs.
Here is an archive copy of Bob Lancaster's Gallery of Unusual Playing-Cards, which included large numbers of links to web sites of playing-card collectors, manufacturers and other relevant information.
Playingcarddecks.com has published a series of articles about playing-cards and their makers and uses.