TMI Source is a fan curated website revolving around the series of novels. It is one of the largest fan-based websites for the content and provides updates on upcoming novels and background information on previously released novels.
A Wiki dedicated solely to the Shadowhunter mythos. Students can find all the in-depth information they'll ever need regarding the universe of Mortal Instruments. Beware, however, because spoilers abound in this site.
Hypable is a third party site that provides information on various works, beyond just Mortal Instruments content. It is a good place to catch up on current news revolving around specific works.
Fangirlish is a third party site that essentially enshrines various works of interest. This link will lead you to the domain regarding The Mortal Instruments, where users can catch up on current news on both the novels and the film.