Does anyone remember the show on discovery channel "Most Evil" ? This psychologist comes up with a scale of ranking murderers and psychopaths. I found it to be pretty interesting and informative. 
01    Those who kill in self-defense and who do not show psychopathic features; these cases do not involve murder.
02    Jealous lovers who kill: These murderers, though egocentric or immature, are not psychopaths. This level on the scale includes crimes of passion.
03    Willing companions of killers: Killers on this level are usually impulse ridden, meaning they have a hard time controlling the kinds of violent thoughts that most people ignore.
04    Criminals who kill in self-defense, but are extremely provocative toward the victim.
05    Traumatized, desperate persons who kill: These murderers may be genuinely remorseful and they lack significant psychopathic traits.
06    Impetuous, hot-headed murderers, who don’t have marked psychopathic features.
07    Highly narcissistic, but not distinctly psychopathic persons, who kill “loved ones” out of jealousy.
08    Non-psychopathic persons with smoldering rage: These people kill when their rage is ignited.
09    Jealous lovers with marked psychopathic features.
10    Non-psychopathic killers who murder people who are “in the way”.
11    Psychopathic killers who murder people “in the way”.
12    Power-hungry psychopaths who kill when cornered.
13    Psychopathic murderers who kill out of rage.
14    Ruthlessly self-centered psychopathic schemers who kill to benefit themselves.
15    Psychopathic spree or multiple murderers.
16    Psychopaths committing multiple vicious acts, which may also include murder.
17    Sexually perverse serial murderers: In males, rape is usually the primary motive and the victim is murdered to hide evidence.
18    Torturer-murderers: Murder is the primary motive and victims are killed after a torture that was not prolonged.
19    Psychopaths driven to terrorism, subjugation, intimidation and rape, but short of murder.
20    Torturer-murderers: Torture is the primary motive with these killers.
21    Psychopaths who do not kill their victims, but do subject them to extreme torture.
22    Psychopaths who inflict extreme torture on their victims and then murder them.
here is a small example:
http://www.youtube.com/watch?v=4pXENo8YePU&feature=fvst