http://dictionary.reference.com/browse/sociopathsociopath: a person, as a psychopathic personality, whose behavior is antisocial and who lacks a sense of moral responsibility or social conscience.
http://dictionary.reference.com/browse/psychopathpsychopath: A person with an antisocial personality disorder, especially one manifested in perverted, criminal, or amoral behavior.
Now for psychopath I chose a definition further down the page since I believe it tends to reflect the difference most people seem to have in understanding the two terms, that is that a psychopath is an antisocial personality with a criminal bent.
On edit, check this link:
http://www.wisegeek.com/what-is-the-difference-between-a-psychopath-and-a-sociopath.htm "What is the Difference Between a Psychopath and a Sociopath?":
Both the psychopath and sociopath fail to feel remorse or guilt. They appear to lack a conscience and are completely self-serving. They routinely disregard rules, social mores and laws, unmindful of putting themselves or others at risk.
Of the more distinguishing traits, some argue the sociopath to be less organized in his or her demeanor, nervous and easily agitated – someone likely living on the fringes of society, without solid or consistent economic support. A sociopath is more likely to spontaneously act out in inappropriate ways without thinking through the consequences.
Conversely, some argue that the psychopath tends to be extremely organized, secretive and manipulative. The outer personality is often charismatic and charming, hiding the real person beneath. Though psychopaths do not feel for others, they can mimic behaviors that make them appear normal. Upon meeting, one would have more of a tendency to trust a psychopath than a sociopath.