Apart from that: metallurgy.
Very few modern things can be made with one's bare hands and without tools. Tools that help build more tools would be essential for re-bootstrapping.
(Chopping the first trees so that you would have something to make fire so you could melt metal would be very hard)
I think energy is the bigger challenge. In Britain in the 1600s, for example, the growth rate of trees couldn't keep up with the demand for charcoal. That was one of the factors that led to the widespread mining of coal, which previously had not been a major energy source in Britain.
The easily mineable fossil fuels are pretty much depleted now. We rely on advanced technology to extract the fossil fuels that power us today. A rebooted civilization might be stuck with charcoal. In which case its energy usage would be capped by the growth rate of the forests.
http://www.eia.gov/energyexplained/index.cfm?page=coal_reser...