VocApp is a free mobile (Android/iOS) app/site that I just found out about from a promotional email, for making multimedia flashcards. This app can be used to learn any subject/topic as a user can create a flashcard containing audio, texts, images, etc. Also, VocApp has some prebuilt courses that are ideal for learning languages (i.e. Spanish). This is a great tool for self paced learning and VocApp differentiates instruction so a student will see items they are having more trouble with.
I highly recommend checking out VocApp by clicking here!!!
For a more detailed review check out Richard Byrne's excellent blog.