For eight years, I've participated in National Novel Writing Month in November. I've only passed the 50,000-word finish line for the last few years, but regardless, I find the experience a great motivator to getting me to write every day. I also love the community of writers that forms through the experience.
The Office of Letters and Light, the organization that hosts NaNoWriMo, kicked off an event last summer that they called "Camp NaNoWriMo", which was a novel-in-a-month event, but in the summer. It's geared toward people who either can't wait until November's event or who don't have the ability to participate in November at all.
They're doing it again this year in June and August. You can sign up at the official site, and there you will eventually be assigned to a "cabin" with 4-6 other writers to cheer each other on, you'll have access to the word count trackers we're familiar with in November, and you'll have the epic motivation that comes from writing a novel in a month with a bunch of other nutcases.
I've signed up to participate in June. I need to get some first drafting done and this seems like as good an excuse as any. I hope all of you will consider joining me on my first summer in Camp NaNoWriMo!