Lafro is a flashcard app with ability to automatically create word lists from a text into many languages. You can also create word lists manually as well as edit the old words and adding new sample sentence to an existing word. By answering simple questions about each word, Lafro figures if you have learnt the new word or not. Please take a look at the tutorial at Lafro website.
Lafro also include 1600 german words with english translation.
In order to unlock the first german word list go to add word list from text section and in the text box simply type "1" and then press next to have the "1" german word list added. You can enter "1" to "16" for all 16 german word lists.