If, like me, you are disciple of what I think we can unblushingly call the Simmons School of Constraint Writing, then I think you might be interested in these two relatively new tools, that could just tie you up in liberation.
1) 750 words
Which allows you the chance to do exactly that. Write 750 words every day. The impulse is rather like that of writing your dream diary or sleep download the moment you wake up.
What makes the site tremendously effective and addictive are the gaming elements that are baked into it. You get badges for the more days that you tot up without a break, stars if you manage to complete your entry without distractions, and crude analysis engine give you a measure of what your subconscious is saying and how fast you're writing compared to other people. I broke my streak the other day, by dint of getting my timing wrong, and the empty space is so disheartening that I haven't written there since.
Yes, it can have that sort of impact.
And why the number? Because apparently it equals about three pages. And we can all manage that every day, can't we?
2) 6 minute stories
Slightly easier on the fingers and the soul; log in, you get a prompt, and away you go. Beware the timing issue again, as you need to give your story titles and tags within the six minutes too. As a flash fiction generator, it's great.