Friday 7/27/12 evening - started coding the backend text message routing logic and the website front (standard stuff - Node.js, custom MVC framework, Twilio API, MongoDB, Redis, Heroku, etc. - the works)
Tuesday 76/31/12 late night - Feature complete, things are all good to go and working (including edge cases, etc.)
Wednesday 8/1/12 - Built out Open Graph integrations, made minor tweaks, chose the name and bought the domain, some branding stuff (i.e. the chinchilla logo), submitted Open Graph actions to Facebook
Thursday 8/2/12 afternoon - Open Graph is all approved, did a test launch with a small set of users, ironed out a ton of bugs
Thursday 8/2/12 evening - posted on HN, making a huge list of things to do next, getting good feedback, and setting up all our other distribution techniques to be fired off tomorrow
6 days from idea to launch! We tried hard to go as fast as possible on this one (although we overbuilt a couple features that we've retracted for the launch - could've saved us a day of work if we had realized they weren't necessary).
[edited to correct the months on the dates]