Phone cards, telecards, telephone cards - however you want to refer to them - are some of the most widely sought collectibles of the last 25 years. First issued in Italy in 1976 http://www.all-cards.net/all.cards/index2.html, the usually plastic cards are now found everywhere from Aland (Finland) to Zimbabwe.

In many ways the ubiquitous cards are similar to postage stamps, with many of the same factors influencing value.

Like stamps, they are printed in varying numbers. Some issues, such as promotional or commemorative cards, can be extremely limited in number, forcing values up. Others are often available in such quantity over such a wide area that obtaining a mint specimen poses no problem whatsoever.

Then, there are technical aspects - type of data storage system, position of magnetic strip, etc. - that are of concern to some card collectors, just as some philatelists are obsessed with water marks and perforation counts.

Finally, the cards have been printed in such tremendous variety that, like philatelists, card collectors can specialize. Some concentrate on first issues. Others prefer pop culture icons like Disney, Coca-Cola, or Star Trek (my favorite, of course). Some people just pick a favorite theme, like flowers, animals, or scenic designs, around which to build a collection.

As in any area of collecting, knowledge of your subject and the protection of your items are two of your most valuable assets. There are a number of companies that offer archival (non-PVC) quality sleeves and albums, some especially for telephone cards. (Phone cards can also safely be stored in non-PVC trading or baseball card sleeves.)

http://www.collecting-supplies.com/welcome2.html
http://www.auctionbytes.com/bin/bizdirectory/biz-dir-index.pl

And for more information on this subject, I recommend the following Web Sites:

http://www.all-cards.net/all.cards
One of the larger sites. Includes card auctions. (Access was easier for me through ENTER, and not through the list of contents at the bottom of their home page.)

http://www.geocities.com/Tokyo/2912/wlfdenwa.html
The hobby from the perspective of a collector of Japanese cards.

http://www.active-phone-calling-cards.com/collecting_phone_cards.html
Concise list of features important to collectors

http://dir.yahoo.com/Recreation/Hobbies/Collecting/Cards/Phone_Cards

Site listings

http://www.eyersworld.com/index.htm
Dealer also provides help pages for beginning and advanced collectors

http://www.hmt.com/phonecards/americards/collecting.html
"Dollars and Cents of Telecard Collecting"

http://directory.google.com/Top/Recreation/Collecting/Phonecards/Organizations
Web Pages

Books

H & G Standard Catalogue of USA Telephone Cards: Including Canada: 1995-1996, by S. E. R. Hiscocks, C. M. Garibaldi
http://www.amazon.com/exec/obidos/ASIN/0964860503/auctionbytescom

Telephone Cards (1999), by Yves Arden
http://www.amazon.com/exec/obidos/ASIN/074780253X/auctionbytescom

Happy hunting!