Well, the Holy Bible makes a distinction between the two. There's a verse that says the Word of God cuts apart the division of soul and spirit. I've been taught that the soul consists of your mind, will, and emotions whereas the spirit is the energy of life that flows through you.
Ironically, when looking up "soul" in the Strong's Exhaustive Concordance (Greek and Hebrew Lexicon), it defines it as "spirit". Furthermore, when a person becomes truly born-again, his or her spirit connects and communes with God's spirit and often times the spirit seems to have a deep sense or cognitive ability (more than just an energy flow).
So my understanding that the spirit as an energy of life may be way off or else not entirely complete. Or it could be that they are different yet intertwined like the scull and brain make up the head.
UPDATE: Another good point by starjumper. Another definition, or rather synonym, for spirit is ghost or angel. Also, when God breathed life into Adam, he became a living "soul". Maybe "life" and "living" are what define spirit.