Teach Yourself Hindi Dictionary provides a comprehensive vocabulary and a concise grammar section. Idiomatic usage is also covered to create a dictionary that is easy to use.
Am currently using this to learn Hindi, slowly but surely. Am actually creating my own dictionary - first was hand written, but now have started using Baraha to do it on the computer. Very time intensive! But I want to have a dictionary that includes word origins and word usages, just like a high-end english dictionary. And the process of creating it is of course a useful learning process. Just wish I could have more lifetimes to live, one is too restrictive! Anyway, this one is pretty good I guess (don't really know enough to judge), their use of transliteration is inconsistent, which is among the reasons I'm creating my own.