Magic: the Gathering* is a collectable trading-card game produced by Wizards of the Coast. Players collect cards and build decks to take part in the game, representing a battle between mages using magical forces to defeat opponents.
The NetRep position involves answering rules questions and raising any rules issues that arise on the group for discussion among various knowledgable folks. The query tracker lists the current open queries, and the rec.games.trading-cards.magic.rules FAQ contains answers to some of the questions that are often asked about the rules of Magic: the Gathering.
Wizards of the Coast produce individual set FAQs to go with each set release, to explain new abilities and particular card interactions. The following are links to local copies that have been reformatted for ease of use:
Here in York we've come up with a few neat things, such as our list of random effects to add to Magic games (kind of supplanted by the new Planechase cards, though), and our own version of Mental Magic. For casual games in York, try the Sci-Fi and Fantasy Society social on a Thursday evening in Derwent College during term-time. For something more serious, do get in touch with me or with the society, and we can probably point you at something appropriate.