Flashcards [⁛] allows you to create a class (in the free version you can have up to 30 students and 5 decks at a time). The students can join your class for free and copy the decks you have created. I start all of my decks with the root word on the front and the definition on the back. Students then add a reminding word on the front. On the back, they add a sentence and a picture (they can choose to draw or find a picture from their camera roll).
That is just where the vocabulary practice starts. Once students are done, there are many games the students can play. In the free version, that can be games like matching, true/false, and a crossword. In the paid version ($29.99), you get 100 Students and 75mb of server space - along with games like Flappy Dog and Ninja! Students can also do Q-Battle and practice their vocabulary words in a competition.
When students practice on their own deck, they get to see the sentence and drawings they created. After they feel like they know the words, I have them practice on the class deck where they just see the root word and definition. This also allows them to compete and be on the top of the class leader board:
Oh! We also made little avatars using Buddy Poke!