http://archiveofourown.org/ :A place for fanfiction writers to flourish. There are numerous different genres to write in, whether you are a fan of a film, tv programme, musician, book, comic book or cartoon.
http://blog.nanowrimo.org/ :It offers inspiration and motivation when you get stuck in the middle of writer's block. There are lots of writers on the site, who will offer advice about practical things
such as how to approach a publisher when you are close to finishing the book.