In the US it's generally appropriate to acknowledge your team and your appreciation of them with a brief email. This also serves to let everyone know that you're not going to be around anymore in case they otherwise missed the memo.
As far as gifting is concerned. There's no hard-and-fast rule on it. It will depend heavily on your office culture, and how close you are with your coworkers.
It's not uncommon to bring in some food to share on your last day, such as doughnuts or cupcakes (If you're of age, and your office tolerates it, it's also not uncommon to bring beer at the end of your last day).
Gifting items to specific people isn't overly common and should really be reserved for anyone who you want to show appreciation to. Basically, only give someone a gift when you would have otherwise given them a gift even if you weren't leaving.
With that said, it's not uncommon for interns to give out random tchotchkes or other mementos. My desk is littered with various things gifted from past interns, such as figurines, kazoos, origami, and a small flock of rubber ducks (for debugging of course). Mostly these related in one way or another to some sort of inside joke or activity.
With the dozens of interns I've worked with, I've never been given a card. I feel that cards are generally reserved for more formal and personal occasions, such as birthdays, weddings, babies, and funerals (boy did that escalate quickly). It would probably be a bit weird, so I'd definitely suggest sticking with a nice email.
Oh, and don't forget the doughnuts.