Guild Wars 2's Black Lion Trading Company offers more than just a way to buy and sell in-game items; it's also used to buy the game's currency known as gems. These gems can be bought and traded for real money and converted to in-game gold for the purchase of just about anything your Tyrian heart desires.
But now ArenaNet is making it even easier to buy the in-game currency through gem cards available for purchase at your favorite retail store. These cards would be perfect as a gift from your grandmother or sweet aunt Vickie, who can help support your crafting obsession without even knowing it. Just tell them that you're really interested in Geology and Gemology. It's a win-win!
[Update: ANet has just posted the complete list of retailers offering gem cards. In the US, they are Fred Meyer, Hasting, NewEgg, Fry's, and Amazon.]