Flippity is a service that allows you to create and share digital flashcards through a Google Spreadsheet. There are many advantages to using a Google Spreadsheet as the content holder for the flashcards. Flippity makes use of them all. While it would be easy for a teacher to setup and fill the content of the course for the spreadsheet, it also could be collaboratively created by students in the class. The creation of several spreadsheets for a study tool might be something that groups who finish work early complete, then share with a teacher who creates a Flippity card set for the rest of the class. In addition to the ability to create the content easily, Flippity allows the creator to add media such as YouTube and images to the card deck. Here's an example of a few cards created using the Spanish word for "Cat" and a picture of a cat.
I've created a quick tutorial on YouTube of this resource to show you how easy it is to create a Flippity deck.