Embodied energy is the amount of energy that goes into a product during its entire life-cycle. It includes the energy required to mine and refine materials, assemble these into the final product, transport it to the consumer, and dispose of it. An analysis that considers this entire process is called a life-cycle analysis.
A 1-litre plastic (PET) bottle has an embodied energy of roughly 5.4 MJ. This is the same as leaving a 15 W lightbulb on for 100 hours (1 kilowatt-hour is 3.6 MJ, a 15 W CFL lightbulb gives light equivalent to a 75 W incandescent light bulb). Aluminium cans are about 1.7x worse than plastic bottles in this respect.
Recycling changes the picture a little. Recycled PET has an embodied energy about 20-25% lower than virgin PET. Other types of plastic can achieve reductions in embodied energy of up to 50% by recycling.
While recycling can reduce the impact of disposables (and keeps the plastic out of landfills and nature), the impact of recycled materials is still huge. Avoid disposables whenever possible!
Source: The ImpEE Project, The University of Cambridge, Recycling Plastic