Is there an official standard vegan packaging symbol designating that a product is vegan?
There are two common symbols; the European Vegetarian Union (EVU) and Vegan Action. 




In my experience, you will see the EVU on packaging and on restaurant menus. I've only ever seen the Vegan Action symbol on packaged products.

The EVU is not exclusively vegan so you'll still need to read the packaging or ask about ingredients if in a restaurant. The Vegan Action symbol is exclusively vegan and is becoming very popular in the United States.