Paul Krugman: Running Out of Planet to Exploit. Starting to lean towards peak oil and other theories that posit some significant problems in the near future due to our limits at expanding and utilizing critical resources. Further note in his blog here, where he goes back to research he did in the 1970s: "But anyway, while the Limits of Growth stuff of the 1970s was a mess, the history of energy technology doesn't support extreme optimism, either."

Andrew Leonard: Malthus is in the air. Cites the Krugman column. Krugman's blog has a previous entry on Malthus, and I don't think that's the only place I've run across the name lately. Leonard has a later post called "Total systematic breakdown, then and now," where he posits analogies between 17th century China and the here and now.