I've always been a fan of tart wines, those palate cleansing and refreshing wines we often don't take as "serious" wines because they don't age well. But, if you like food, a vibrant wine like Vinho Verde, literally "green wine" but referring to the freshness rather than the color, can be perfect, especially in the heat of summer.
I'd tasted Vinho Verde in California and liked it, despite the fact there's not a great supply of it here. But having it in northern Portugal is a whole different thing. It suits the land and the food.
Vinho Verde even comes in a red version, which was news to me until the maître d' of the Pousada de Santa Maria do Bouro near Amares (book direct or see information) brought us a couple of glasses to try. Excellent and unpretentious wine. By the way, the Pousada, a restored 12th century Cistercian monastery, is incredibly evocative to stay and wander around in (see the courtyard above), and warrants its 9.9 of 10 user rating, unusually high these picky days.
About.com has prepared a video to educate you on this unique wine: Quick Tip: What Is Vinho Verde?
The north of Portugal is a beautiful and intriguing place. You should go.