1. Ethics and "ClimateGate": An interesting post by Aswat Damodaran on the ideal and real academia.
2. What is the LaTeX symbol for that? A older link, but interesting, if you haven't seen this before.
3. Yet another beautiful proof of the irrationality of the square root of 2.
4. Along similar lines, Euclid's elegant proof of "there are infinite prime numbers" in the Kumari Meera Memorial Lecture by M. S. Raghunathan (via this link).