Flash drive recovery software for SD memory card?

[Robert La Ferla]

I have a SD memory card that I used to take several photos on.  I know  
that the camera stored the photos on the disk because I reviewed  
them.  When I went to transfer the photos to my computer (via a USB  
cable), my Macbook didn't mount my camera.  I unplugged the cable and  
got an unsafe device removal error.  I then tried mounting the device  
on a Windows PC but it can't read the disk.  Is there some free or  
open source utility for any platform that can help me recover my "once  
in a lifetime" photos.

Thanks,
Robert