Suggestion: Flash cards
It would be great to have a way to just run through the words in any given chapter and just worry about remembering their meaning without any greater context. A really quick practice. Failing that, perhaps give us the ability to export the words from each section to make our own flash cards. Whether it's CSV or XLS or whatever.
I think the "export" idea is a great one.
As for the flashcards, I honestly don't want it. There are a ton of really specialized Flash Card sites out there atm, and some great Flash Card mobile/PC software (Anki), and I don't think Duolingo should be allocating time to reinvent the wheel.
I would agree, however having something built into the site to adapt to new words as you learn more would be better than having to export a new list every time you learn more words. Plus, in my opinion, this would be an incredibly trivial feature to add. There would be next to no reinventing necessary. They already pull the words and their definitions for the vocabulary pag; it should be a simple matter to just create a small jquery applet to provide some show/hide, previous/next functionality.
I'm only really speaking about a base flashcard application, not something tied to the site's "scoring". If you don't integrate it into the scoring system then coding a small application to do this should literally not take more than a few hours. If you want to integrate it into the scoring system then I agree that it might be more trouble than it's worth.
I'm not in favour of adding scoring to this, but I can imagine that if duolongo wants to enhance their site they might want to code it to the same standards as their other quiz material so it fits in with the "feel" of the site.
Either way, I think it would be a great addition :)
I would appreciate flashcards incorporated in Duolingo's fun experience and beautiful interface. Of course export is good, too, and even without it we can copy new words to any flashcard app we like, but having ready-made Duolingo flashcards and getting Duolingo points for flashcard practice would be really cool.