Has anyone tried memrise.com for learning languages? It allows users to create flashcard-like courses for learning all sorts of things, and includes courses for the major Indian languages. It is available as a website and through free iPhone and Android apps. You have to sign up to use it, but some of the Hindi courses look useful for improving vocabulary, so it might be worthwhile trying out. But it does get difficult when they test your English -> Hindi knowledge and expect you to type in अलमारी quickly using an onscreen Devnagari keyboard.
Following up on my own post: it turns out that the iPhone app does not display Devnagari very well. You can usually guess at what it's supposed to be saying, but only if you already read the script and know the words reasonably well. That's quite a black mark against Memrise, as it could have been great for commuting on the train.