There are three types of Harry Potter cards available. The first is the Harry Potter Trading Card Game, which Wizards of the Coast put out a few years ago. It was a really spectacular game, somewhat similar to Magic. The game was going strong and doing well until Yu-Gi-Oh came along. The game was discontinued a year later at a most unfortunate point, since a new series had just been released to coincide with the release of the second film and several of the cards in that series were broken (which means they allowed for unfair play). Typically, broken cards in a trading card game are fixed in the next series released, but there never was another series and so the final version of the game can be unplayable in some instances. The cards for this game contain a lot of new information, including the first names of some characters, but we still haven't been able to determine how much input Rowling had into them, so they remain non-canon.
I have talked with Wizards of the Coast about this and all they are allowed to say is that Rowling worked with their people to assure the accuracy of the information. I have since learned from them and from the folks at Electronic Arts that companies which create Harry Potter information are forbidden by contract to claim to present "new Harry Potter information." In other words, they can't say that their product is canon, even if it is by our definition.
The second type of Harry Potter cards were trading cards with photos from the films. These cards offer no additional information, they're basically souvenirs of the films, and the films definitely aren't canon.
The third type of cards are the Famous Wizard cards, the ones Jo was talking about on her site. These cards have appeared in several forms. They are included in the candy Chocolate Frogs you can buy in the store (and there are several series of these cards, some created by none other than Wizards of the Coast, which strongly suggests a link between them and the Trading Card Game). They also appear in the Electronic Arts video games, and it is from those games that we get the entire list of 101 cards.
Jo has been using the information from the Famous Wizard/Chocolate Frog cards for her website's Wizard of the Month. You can read the entire list of cards on the Lexicon (see). In order to gather all available data, we had to track down each card from each source, since some include additional details that others don't have. The Lexicon has the complete and ultimate list of all that information, information which we now know is canon.
For many of the cards we also include scans of the cards themselves, and the artwork is in some cases quite amazing. We haven't been able to include any of the Electronic Arts images yet, although I've been asking them for permission to use those graphics for two years. I have all the images...just can't use them as yet.
In order to find scans of card images, click on any of the links on the page given above to go to the Which Wizard section of the Lexicon. Image links are available there.
Steve Vander Ark