National Novel Writing Month is an annual internet-based creative writing project which challenges participants to write 50,000 words of a new novel between November 1 and November 30. The project started in July 1999 with just 21 participants, but by the 2010 event over 200,000 people took part - writing a total of over 2.8 billion words. [Source: Wikipedia]
Script Frenzy is an international screenwriting challenge which began in June 2007. Participants attempt to write a script, usually a screenplay or stage play, of a given minimum length in a single 30-day month. [Source: Wikipedia]
KG.de is a german forum for writers, readers and reviewers of short stories.