There's a good chance the pictures are recoverable after deletions or formats of a memory card from a camera. First, don't use that card in any camera or write into it. Take it out and label it in an envelop.
Google or yahoo "image recovery". You will get many links to software that does image recovery. Select one and download a trial version, install it and have it scan the card. Most likely, you will be able to recover some of the pictures.
If you have an external reader, run the image recovery software against it. If you connect your camera to your computer to download, most likely, the camera's storage will show up as a drive when you connect, in that case, point the software to the drive that was created when you connect your camera. The image recovery software will scan the entire card and restore deleted picture to another location (your hard drive) if it finds any. If you have any questions, let me know.
I've recovered many pictures this way for friends and others. As long as you haven't taken more pictures or write to the card since you format it, there is almost 100% chance of recover. Even if you've written to it, not all pictures are lost, just the one that was written over.