http://www.economist.com/ - my second best feed (after HN)
Occasionally:
http://www.datatau.com/ - HN for data science
https://johncarlosbaez.wordpress.com/ - Mathematics, Theoretical Physics
https://terrytao.wordpress.com/ - Mathematics
http://slatestarcodex.com/ - Less Wrong-kind stuff (the guy writes frequent and well, but somehow too verbosely)
http://visualizing.org/ - data visualizations
A bit of G+ (mainly, if not only, for a few guys in mathematics and physics).
http://www.economist.com/ - my second best feed (after HN)
Occasionally:
http://www.datatau.com/ - HN for data science
https://johncarlosbaez.wordpress.com/ - Mathematics, Theoretical Physics
https://terrytao.wordpress.com/ - Mathematics
http://slatestarcodex.com/ - Less Wrong-kind stuff (the guy writes frequent and well, but somehow too verbosely)
http://visualizing.org/ - data visualizations
A bit of G+ (mainly, if not only, for a few guys in mathematics and physics).