I have just gone through this exercise.. same disk.. same problem.. perhaps worse than yours as the drive would not mount.. it corrupted the data partition.
I downloaded the trial version of data rescue 3 and running that I could see the files.. you need a target disk to copy the files to.. and pay for the full version.. $99.
The most popular tool is diskwarrior. I could not find a demo so didn't want to pay $99 to discover it cannot recover.. it depends.. how important is your data.
I did find you can create an image using ubuntu boot disk.. that was hard to setup though but did work. Unless you like command line stuff.. I cannot recommend you do that.. it is too easy to damage things.
So as I said at first.. get a tool. If you already tried disk utility and it fails.. that is where the paid tools come in.
Most people commend diskwarrior..
There is no guarantee .. no refund if it fails.. but have a go, I think it will help.
Or data rescue or disk genius.. but the disk warrior did seem to generally be the standard for mac.