Do not reformat the card!
*EDIT: Okay...just wanted to get that in first. I can't recommend any software in particular, but a google search for picture recovery program should do the trick...there are several.
Did you delete them on your computer screen? If so, they may be in the trash.
I mean, was the camera linked to your computer and where you browsing the images on the camera's card through the finder on your computer. When I delete images from my camera I do it through the computer after I dump the images. Once I verify that the images did copy onto the computer I then reformat the card.from my camera not computer?