Scikit-Learn

I have been having a lot of fun in 2013 using scikit-learn with the ipython notebook interface. It seems that most of the things that drive me bonkers about R are easier in scikit-learn. The ipython notebook makes a beautiful IDE that allows for interactive open science notebook development. It allows for easy notes, videos, links, pictures.
Meanwhile scikit-learn allows for a nice, consistent set of interfaces for most supervised, unsupervised and feature selection tasks. The tutorials are great, but even better are the online videos from pycon2013 and SciPy2013.
http://scikit-learn.org/stable/