There are different styles of flash cards available, based on how masochistic you feel:

• Easy Flash Cards uses random selection to pick out words, making it easy to guess words for polysynthetic languages once you develop familiarity with common roots.
• Hard Flash Cards uses a Levenshtein-based method to pick wrong answers in order to make them look more similar to the correct answer. This is good if you're practised with the language and want to learn how to stop conflating similar words, but it is cheatable by looking for the "centre" word that the others are all misspellings of. (It also tends to resort to words with the wrong part of speech, making things easier to pick out.) It may crash if presented with a dictionary with parts of speech that have very few words in them, and is generally slow.
• Coming soon: Unforgivable Betrayal Flash Cards, which will actually generate typos of words for alternatives in order to make your life worse.
• Related: Sentence Sandbox, a tool that generates random sentences (with hover-to-define glosses) in Zeyetaní Lilitika and underlines subclauses to improve reading comprehension.