Includes lots of activities/exercises by level, ranging from A1 to C2; material especially tailored towards the official DELE diplomas; articles on Spanish grammar, vocabulary, music, cinema, Hispanic culture, and more.
The Royal Spanish Language Academy offers a free, extremely comprehensive dictionary online. Additionally, if you look up a verb, a ‘conjugar’ link is supplied for you to check all of the tenses - this way you can recognize stem changes, irregular verbs and patterns.
Although there are many translation sites, this one is interesting because it adds many of the use of words in idiomatic expressions and formulaic language. It also includes a forum where specific constructions are addressed.