This was inspired by a conversation with a student from Germany who isn't in my Spanish class, about how to teach vocabulary in a World Languages course.
I don't use flash cards most of the time. I try to incorporate communicative activities in my classroom as much as possible. So I try to avoid using "memorize the Spanish word / memorize the English translation" activities as much as possible. My students still have a vocab list with the Spanish on one side and the English on another, because they get nervous if they can't see their vocabulary. But I use it as a security blanket, not as a primary source of vocabulary. (That's the intent, at least.) I see flashcards, as a rule, as an extension of memorizing translations. Studies show that this is an ineffective method of learning a language over the long term.
Instead, my students do glossary entries--they write the Spanish word and its translation, write a definition in Spanish or use the word in an example sentence, and draw a picture that illustrates the word. The idea is that by using the word in a meaningful sentence, they give it a meaningful context; by drawing a picture of it, they engage in non-lingustic representation, which helps with both retention and contextualization. I'll try to find the research on non-linguistic representation on vocabulary. The research is on the effects of vocabulary on L1 content learning, but it makes sense that L1 vocabulary acquisition strategies would work on L2 vocabulary, as well. The idea is that the students do one of these a day.
But this student, who learned English in Germany before coming to the United States, suggests a mechanism for using flash cards of the "L2-on-one-side-L1-on-the-other" effectively. It works like this--The student gets a box with 5 numbered compartments and 10 vocab cards. You run through the vocab, and every word you can translate and pronounce correctly moves up a compartment. Every day 10 or so new vocabulary cards go into Compartment 1. You study Compartment 1 every day, moving cards you know up. Compartment 2 gets studied every other day, with cards moving up as you go. Compartment 3 gets studied every week; compartment 4, every other week; Compartment 5, every month. After you know the vocabulary from Compartment 5, you can throw the card away, because you know the vocabulary forever.
Comparisons: If done correctly, both of these methods have students spending 10 minutes a day studying vocabulary, which is extremely helpful for long-term acquisition. (Source needed.)
Contrasts: The flash card box has a mechanism for revisiting old vocabulary; I ask my students to revisit their glossary, but have no way of making sure they do. The flash cards ask students to memorize vocbulary, while the glossaries ask them to use the vocabulary. Flashcards have students going over a large number of words each day, while glossary entries ask students to go over one word and use it in 3 different ways (including the one I purport to reject as effective). lashcards focus on 1-word-at-a-time acquisition, while glossaries ask students to use the words in sentences. The flashcard box places a specific value on knowing how to pronounce the words for advancement, and the glossaries do not.
Refinements: Flashcards could include pictures instead of words, where practical. (Turns out it's tough to draw a picture that represents conjunctions and words like "however.") I could include vocab quizzes for glossary entries, or some ongoing showing-off-glossary-entry speaking projects. Both projects could be modified to make them computer-based; this would use less paper and increase useability, but then accessibility would be a factor.
Mini-study idea: While presenting new vocabulary, half the class gets a flash card box and half the class gets a refined glossary entry project, with a limited set of vocabulary to choose from. Each assigment should be filled daily, and appropriate controls are put it to encourage and enforce compliance--the teacher checks the flash card box for changes, and checks in glossary entries, every day. After 1 week, the students take a vocabulary test that focuses on students' abilities to comprehend vocabulary; resulsts are compared. The test is re-administered after another week, and 1 month after the beginning date of the project, to test long-term retention.