I'm a big fan of the
AllSet Learning Grammar Wiki, and one of the most useful things I've come across on there is a few pages that list Chinese grammatical points according to their European Common Framework level. These six levels
roughly correspond to the six levels of the New HSK, so it would be a good idea for someone studying for the HSK to ensure that they are familiar with all of the grammar points at their level and below. Each list of grammatical points links to a page with more explanations and examples, a really great resource! I have noted the corresponding HSK levels for each page.