My son is 8 years old. He loves cards. Mainly those Yugio things that I can't even come close to spelling right. LOL But he is also into Star Wars so I bought him a pack of Star Wars cards. He doesn't play any games with them but he really does enjoy laying them all out and then putting them back into his collecter book.
My son also enjoys legos. They have all kinds of really neat kits now. They aren't cheap. Usually $8.00 for a small one and up around $100.00 for the really large ones. But you can find a lot in between prices. They have Star Wars, Pirates of the Carribean, Police cars, and lots of other things to build.
Sorry I can't help you with a girl. The first girl to be born into our group of friends is less then 2 weeks old. LOL So I am unsure about what girls like!