Paul Krugman writes about rising food and energy prices today in his column, and he thinks they are the result of significantly increased worldwide demand that has not yet (and which may never be) matched by an increase in supply. The third possibility he sees is that speculators are just betting, incorrectly, on higher prices. Apparently Warren Buffett believes that to be the main reason for recent price increases.
The reigning expert regarding resource constraints on economic growth is Yale's William Nordhaus. I haven't seen any research recently that suggests rapid world growth, centered in China and to some extent India, will dwindle resources so much to create a significant drag.