Simply Statistics1: Written by the Biostatistics professors at Johns Hopkins University who also run Coursera's Data Science Specialization
yhat's blog: Beginner-friendly content, usually in Python
No Free Hunch1 (Kaggle's blog): Mostly interviews with competition winners, or updates on their competitions
FastML: Various machine learning content, often with code
Edwin Chen: Infrequently updated, but long and thoughtful pieces
FiveThirtyEight: Tons of timely data-related content
Machine Learning Mastery: Frequent posts on machine learning, very accessible
Data School: Kevin Markham's blog! Beginner-focused, with reference guides and videos
MLWave: Detailed posts on Kaggle competitions, by a Kaggle Master
Data Science 101: Short, frequent content about all aspects of data science
ML in the Valley: Thoughtful pieces by the Director of Analytics at Codecademy
Aggregators
DataTau: Like Hacker News, but for data
MachineLearning on reddit: Very active subreddit
Quora's Machine Learning section: Lots of interesting Q&A
Quora's Data Science topic FAQ
KDnuggets: Data mining news, jobs, classes and more
DC Data Groups
Data Community DC: Coordinates six local data-related meetup groups
District Data Labs: Offers courses and other projects to local data scientists
Online Classes
Coursera's Data Science Specialization: Nine courses (running every month) and a Capstone project, taught in R
Stanford's Statistical Learning: By the authors of An Introduction to Statistical Learning and Elements of Statistical Learning, taught in R, highly recommended, running January through April 2015 (preview thelecture videos)
Coursera's Machine Learning (Andrew Ng): Andrew Ng's acclaimed course, taught in MATLAB/Octave (preview the lecture videos)
Coursera's Machine Learning (Pedro Domingos): No upcoming sessions (preview the lecture videos)
Caltech's Learning from Data: Widely praised, not language-specific
Udacity's Data Analyst Nanodegree: Project-based curriculum using Python, R, MapReduce, MongoDB
Coursera's Data Mining Specialization: Brand new specialization beginning February 2015
Coursera's Natural Language Processing: No upcoming sessions, but lectures and slides are available
SlideRule's Data Analysis Learning Path: Curated content from various online classes
Udacity's Intro to Artificial Intelligence: Taught by Peter Norvig and Sebastian Thrun
Coursera's Neural Networks for Machine Learning: Taught by Geoffrey Hinton, no upcoming sessions
statistics.com: Many online courses in data science
CourseTalk: Read reviews of online courses
Online Content from Offline Classes
Harvard's CS109 Data Science: Similar topics as General Assembly's course
Columbia's Data Mining Class: Excellent slides
Harvard's CS171 Visualization: Includes programming in D3
Face-to-Face Educational Programs
Comparison of data science bootcamps: Up-to-date list maintained by a Zipfian Academy graduate
The Complete List of Data Science Bootcamps & Fellowships
Zipfian Academy: Offers Data Science Immersive, Data Engineering Immersive, Master's in Big Data (San Francisco, but possibly expanding)
Data Science Retreat: Primarily uses R (Berlin)
Metis Data Science Bootcamp: Newer bootcamp (New York)
Persontyle: Various course offerings (based in London)
Software Carpentry: Two-day workshops, primarily for researchers and hosted by universities (worldwide)
Colleges and Universities with Data Science Degrees
Conferences
Knowledge Discovery and Data Mining (KDD): Hosted by ACM
O'Reilly Strata + Hadoop World: Big focus on "big data" (San Jose, London, New York)
PyData: For developers and users of Python data tools (worldwide)
PyCon: For developers and users of Python (Montreal in April 2015)
Books
An Introduction to Statistical Learning with Applications in R (free PDF)
Elements of Statistical Learning (free PDF)
Think Stats (free PDF or HTML)
Mining of Massive Datasets (free PDF)
Python for Informatics (free PDF or HTML)
Statistics: Methods and Applications (free HTML)
Python for Data Analysis
Data Smart: Using Data Science to Transform Information into Insight
Sams Teach Yourself SQL in 10 Minutes
Other Resources
Open Source Data Science Masters: Huge list of resources
Data Science Trello Board: Another list of resources
The Hitchhiker's Guide to Python: Online guide to understanding Python and getting good at it
Python Reference: Python tips, tutorials, and more
videolectures.net: Tons of academic videos
Metacademy: Quick summary of many machine learning terms, with links to resources for learning more