Clary:

a story about an artist with loads of technical artsy details about the paintings the main character create which become long and tedious. Jocelyn's the only person who ever reads the whole description

Jace:

Begins by writing a hardcore action adventure novel with demons and Zombies and bloody battles, but then adds a little romance and before long it's a full out cutsey romance novel

Izzy:

Smutty romance

Alec:

secret account with rants, hate on Jace and also where he writes his personal journey, but no ones found out about that... Yet...

Simon:

Gaming fanfiction, but also a music related story which is based around his band

Magnus:

Really detailed, long and popular series which actually has really good quality writing. No one took Magnus as a writes, but it turns out he's really good at it. Also Malec fanfiction.

Jocelyn:

Painting tips, Q and As and advice in agony aunt style

Maia:

Supernatural stories with Vampires and Werewolves and loads of drama