Experience with SD-card image recovery software?

The SD-card from my Casio digital camera is apparently corrupted in some way. The camera says "Card ERROR" and when trying to read it on my computer it says "Device is not formatted". I have just learned here that there is software available to hopefully recover the images. My question is do any of you have experience with this type of software and can you recommend a product? It would be nice if it were free, but I am willing to invest if necessary to recover the pictures that were taken while on vacation. Thanks, Jim