Gift cards and clothes, when I can afford to get people gifts at all. I never know what to get people, so it's usually gift cards and clothes. Gift cards may be a bit impersonal, but you can get whatever you want with them, and you never truly appreciate clothing as a gift until you grow up and/or reach a point where you can't afford to buy clothes.
As for receiving; bookstore gift cards, clothing, and coffee mugs.
Also what honeymilk said, kitchen stuff.