I'm not just saying this because Jason is a good buddy of mine, but this is an excellent walk-through of Django. If you're building a web app and had a nagging curiosity in Django, this one will get you going.
Why is this here though? This is more of a reddit article, isn't it? What does "How to build a simple blog application using Django" have to do with startups?
Django makes it very easy to have something working up and running right away and has a fair number of advantages that go along with it. After looking over languages and frameworks it is what I've picked to write any future web app in. I've yet to see anything more compelling.
A nice tutorial and walk through is a good way to get your feet wet with a framework and language. You have to build a site using something and have to start somewhere. Because of Django, and lack of sleep, imageboard.net was up and working in a single weekend. It's worth checking out.
