virgin strawberry daiquiri. tastes delicious (especially with whip cream on top), and no one will question if you're drinking or not. ok, thats a girly drink, so maybe if you're a guy, juice? or virgin margarita (nice salted rim, or get it sugared - yum).
I enjoy drinking ginger beer which can be purchased as either alcoholic and non-alcoholic. You might also think of trying if you like beer you may consider trying Heineken Blue which is also non-alcoholic.