Is there a list anywhere of which NPC card players and which cards they often use? I'm just re-playing the game after a 100% complete but want to explore the card game a bit more.

There is a guide that gives the name and location of most (if not all) the NPCs that are card players throughout the game and tells whether or not they have rare cards (i.e. characters/GFs) and what rules they use. I didn't read the whole thing, but it appears to be quite thorough. The guide is entitled "Card FAQ (PS) (JP)" and it is done by HJerng and can be found on gamefaqs.com after searching Final Fantasy VIII FAQs on the list of PC games.

In honesty, apart from the rare card holders, most of the NPCs have similar cards. The majority of them have Levels 1-5 cards, very few of them have the boss cards. I haven't got a list, but challenge anyone for Levels 1-5, the first time you can get cards that are Level 6 is Galbadia Garden NPCs I believe, they have Level 6, possibly 7, sorry it's not the clearest information but I haven't played in some time. :)

I know where a lot of the cards are and can guide him to some of them.
Of course:he will have to beat the card queen to get them and that is going to be a pain as its a lot of resets.