1. The economics of principal write-downs.
2. Saturn's Hyperion: a moon with odd craters, more astronomy photos here, via GH.
3. Different ways supermarkets increase their profit margins.
4. What economists know about open source software.
5. Peto's paradox: why is there no correlation between animal body size and cancer?, plus a meditation on blue whales.
6. The new Banerjee-Duflo book.