I think that while there are many other contributing factors to the difference between the 2, these are the most obvious and easily spotted ones:
Envy is the desire to possess what someone else has, it is usually accompanied by feelings of wanting to take it away from them even if it doesn't benefit the envious. An envious person usually gets angry at himself for not possessing that which he desires; he is mad at himself for not having what someone else's does, instead of getting mad at the possessor. An envious person wants to rob the other of their success.
Jealousy, on the other hand, is getting angry at another person for receiving or possessing what he thinks he rightfully deserves. It is not usually the center of the conflict he covets, but rather the position of who won it. For instance, if 2 girls like one guy, and the guy picks one of the girls eliciting jealousy from the other, the resentment is targeted at her competitor for winning, not at the guy she failed to attain.
So... what do you guys think?