I have come across a new scientist article where two scientists did a couple of experiments trying to replicate Benjamin Libet's free will experiment where he concluded that unconscious neural processes determine our actions before we are ever aware of making a decision. His experiment is however called into question by Jeff Miller and Judy Trevena of the University of Otago in Dunedin, New Zealand. They used scalp electrodes, but instead of letting their volunteers decide when to move, Miller and Trevena asked them to wait for an audio tone before deciding whether to tap a key. If Libet's interpretation were correct, Miller reasoned, the readiness potential should be greater after the tone when a person chose to tap the key.
While there was an readiness potential before volunteers made their decision to move, the signal was the same whether or not they elected to tap. Miller concludes that the readiness potential may merely be a sign that the brain is paying attention and does not indicate that a decision has been made.
Miller and Trevena also failed to find evidence of subconscious decision-making in a second experiment. This time they asked volunteers to press a key after the tone, but to decide on the spot whether to use their left or right hand. As movement in the right limbs is related to the brain signals in the left hemisphere and vice versa, they reasoned that if an unconscious process is driving this decision, where it occurs in the brain should depend on which hand is chosen. But they found no such correlation.
You can read about the experiments here
Consciousness and Cognition, DOI: 10.1016/j.concog.2009.08.006; Brass Nature Neuroscience, DOI: 10.1038/nn.2112.