750words.com. This site allows you to do Morning Papers as described in The Artist's Way: A Spiritual Path to Higher Creativity (affiliate link). And I found out about Morning Papers by reading Pam Slim's book Escape from Cubicle Nation: From Corporate Prisoner to Thriving Entrepreneur (affiliate link).
To boil it way down, Morning Papers are three pages of stream-of-consciousness writing. Whatever comes to mind, just write it down. Don't think, just write. And the three pages can be anything. Anything. Part of this is catharsis: things that occupy your mind can be transferred onto paper so that those things won't impede your flow of creativity throughout the day (and this isn't just for artists or just for writers - creativity does not discriminate between vocations).
The magic of 750 words is twofold. First, it digitizes the process. Instead of writing longhand on paper, you're typing on your keyboard into a web-based service. Second, they've gamified the process. There are all sorts of tracking tools such as how many words per minute you wrote, how often you were distracted, how many days in a row you've written 750 words, what your mood was, did you write mostly in past, present, or future tense, and all sorts of fun things. I don't share all of my data, but here is what I've allowed to be publicly available. There are badges you can earn for certain behaviors (fast typing) or streaks (10 days in a row). There are also monthly challenges. For example, today I just signed up for the September challenge that I will do morning papers every day. If I pull it off, I will treat myself to some fine imported German beer. If I fail, I will donate three bucks to 750words. If I make the goal, my name goes on the Wall of Awesomeness and if I don't it will go on the Wall of Shame. The only way to get your name off the Wall of Shame is to accept and complete the challenge some other month.
750words.com is free, though donations are encouraged.
Having started this in August, I can say that it has helped me in general at being more productive throughout the day and helped me get unstuck with my writing. I'm really glad I was told about 750words. It has helped me and I hope it will help you, too.