Ohh--titling is one of my favorite parts. As others have mentioned, song titles are a GREAT source, especially if you mix them up a little. I used "Can't Help Loving That Frog of Mine" instead of "Can't Help Loving That Man of Mine" for example. Also, takes on famous literature or movies make great titles, i.e. "To Have or Have Not" (which I've used) or "It was the Best of Times, It was the Worst of Times" (which I might use one day).
Sometimes, my working title will tell me more about what the story is about until I've nurtured it sufficiently to figure out what the "real" title ought to be. For example, Nicholas Blake (Cecil Day Lewis, the poet laureate of England writing under a pen name) wrote a mystery that was known as "The Corpse in the Snowman," but since the story dealt in large part with the search for the missing person (who turns out to be not only missing, but a corpse inside a snowman), that title wasn't really very effective since it gave the plot away. They changed it in later printings.
Often, the idea for a great story comes from a title. If, for example, I said to you (and all other writers lurking out there) "Hog Wild," I'll bet dollars to donuts that most of us would start smiling immediately and come up with our own unique (although possibly similar) plot line. If I said, ""Rainbow Confection," for example, that might lead you off in an entirely different direction.
Two of my favorite title stories:
#1 There is a book called "Bimbos of the Death Sun" by Sharyn McCrumb. It's a murder mystery set at a science fiction convention. One of the two main characters is a scientist who teaches at a college; he wrote a theorhetical paper about a phenomena he observed and hypothesized on--that the radiation from the sun of a distant planet was having a negative effect on the female population of the planet while the males went relatively unaffected. Since it wasn't hard science, he couldn't publish it as such, but his colleage and friend, a lady who was a big science-fiction reader, encouraged him to have it published. The publisher liked it and said, "What's the title of your story?" He gives them a blank look and said, "Duh, I don't know--YOU title it." So when his book comes out, he is horrified to see that it is titled, "Bimbos of the Death Sun."
#2 I cannot improve upon Wikipedia's description:
The Door into Summer is a science fiction novel by Robert A. Heinlein, originally serialised in The Magazine of Fantasy & Science Fiction (September, October, November 1956, with covers and interior illustrations by Frank Kelly Freas) and published in hardcover in 1957. It is a fast-paced hard science fiction novel, with a key fantastic element, and romantic elements.
The title was triggered by a remark that Heinlein's wife had made; in the novel itself, the protagonist's cat refuses to leave their house through any of its numerous doors when he sees snow on the ground: he is looking for The Door into Summer. Heinlein wrote the complete novel in only 13 days. No rewrite was needed, only some light editing that Heinlein did himself.