LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
Invent With Python - Learn to program Python for free
AlternativeTo - AlternativeTo lets you find apps and software for Windows, Mac, Linux, iPhone, iPad, Android, Android Tablets, Web Apps, Online, Windows Tablets and more by recommending alternatives to apps you already know.
Mode Python Notebooks - Exploratory analysis you can share
JSter - JSter is a community-driven catalog of the most useful javascript libraries.
Learn Python The Hard Way - One of the best guides to learn Python & coding in general