It's a question that hounds us all. Definitely something I've been thinking about for the last several months. The question sucks because there is no answer and everybody knows it, yet we have to live for something, right? …otherwise we might as well be dead.
However, the Partially Examined Life podcast has helped me define the question a little more to my liking. According to the podcast, Freud rephrased the question from "What is the meaning of life?" to "What do you want to get out of life?"
I don't think the questions are equivalent, but I'd much rather spend time trying to answer the second question. It seems to be much more answerable and leaves you accountable for your own life, and it's meaning.