So many great data science/machine learning blogs, so little time!
Company Blogs
http://googleresearch.blogspot.com.au/
https://research.facebook.com/blog/ai/
https://research.facebook.com/blog/datascience/
https://blog.twitter.com/data
http://data.quora.com/
https://engineering.linkedin.com/big-data
http://blog.linkedin.com/topic/economic-graph/
http://www.ebaytechblog.com/category/machine-learning/
http://blogs.aws.amazon.com/bigdata/
http://nerds.airbnb.com/data/
https://codeascraft.com/category/data/ (Etsy)
http://blog.kaggle.com/
Personal Blogs
http://blog.echen.me/ (Edward Chen)
http://fastml.com/ (Zygmunt ZajÄ…c)
http://flowingdata.com/ (Nathan Yau)
http://simplystatistics.org/ (Jeff Leek, Roger Peng, and Rafa Irizarry)
http://hunch.net/ (John Langford et al.)
http://www.walkingrandomly.com/ (Mike Croucher)
Aggregators and other links
http://www.r-bloggers.com/
https://www.reddit.com/r/machinelearning
http://www.datatau.com/
http://stats.stackexchange.com/