The first wave of Enterplay trading cards sold out a month or so back, so they just finished printing up the second edition! They’ll be back on shelves the same places you found them before, and it’s the same cards as before. The first run (first edition) had some spelling, grammar and continuity errors on them, so if you’re huge into having complete card collections, you’re going ot have to pick up this new wave, too.
You can also get a collectors tins of cards at stores, too. Inside the tin is some packs of cards, a list of all the cards, and a promo Twilight Sparkle card. Normally, promo cards are only available at cons, so they’re pretty expensive. Twilight will obviously be a lot cheaper than the others, due to her much easier means of getting her.
You can pick up Enterplay cards in either the pony or collectible card game aisles. They’ve been found at Targets, Walmarts, Toys ‘R Uses and local hobby stores. You can also buy packs of cards on Enterplay’s site.