This is one of the most useful dictionaries online. The fact that it's also linked to 百度百科 (a sort of Chinese Wikipedia), the information available here is next to endless. Since most is in Chinese, this is a pretty good way of combining reading practice with dictionary look-ups. I use it for idioms, fixed expressions, other things I can’t find in other dictionaries.

More information about dictionaries here: 21 essential dictionaries and corpora for learning Chinese.