Flask is a Python microframework deliberately built with a small core and easy-to-extend philosophy. Flask is generally considered more Pythonic than Django because Flask web application code is often more explicit. Flask was also written several years after Django and therefore learned from the Python community's reactions as the framework evolved. Jökull Sólberg wrote a great piece articulating to this effect in his experience switching between Flask and Django.
The 18-part Flask mega tutorial is an absolutely amazing starting resource for using the Flask framework. Yes, there are a lot of posts in the series. However, each post is focused on a single topic to contain the complexity while the reader is learning the framework. The whole series is well worth an in-depth read-through. The author is also writing the O'Reilly Flask Web Development book so consider picking that up as well.
The Flask Extensions Registry is a curated list of the best packages that extend Flask. It's the first location to look through when you're wondering how to do something that's not in the core framework.
Randall Degges wrote a detailed walkthrough for building a Flask app in 30 minutes.
Nice post by Jeff Knupp on Productionizing a Flask App.
Building Websites in Python with Flask is another walkthrough tutorial from first steps through getting bigger with Flask.
The Plank & Whittle blog has two posts, one on Packaging a Flask web app and another on Packaging a Flask app in a Debian package once you've built an app and want to deploy it.
The Tuts+ Flask tutorial is another great walkthrough for getting started with the framework.
Flask by Example: Part 1 shows the basic first steps for setting up a Flask project.
