Have formated in camera? Then chances for recovery are good and searching for recovery tools here will give plenty of results. Just make sure you don't write to the card anymore, even inserting / mounting to computers can result in writing.
If you have formated the card in computer say 'farewell' to your images.
Did you do a Low Level Format? (takes two or three minutes to complete depending on the card size). I imagine most DSLRs today have that feature.
If it's low level, then that might be the end of it. If your camera does not have a Low Level format option, then it's possible that the files were just deleted (happens very fast), and can still be recovered. As Octarine said: "Just make sure you don't write to the card anymore", and attempt to recover.
Some places to find recovery software: download.com, tucows.com > most will let you try, to see that it works, but for full recovery you usually need to pay for the license (I tested two or three then bought one). Anyone have any idea if there's freeware that does this?
AFAIK, memory cards and all newer hard disks don't have this option of Low Level Format anymore. The sectors of the media are managed by the controllers of cards and HDD and if sectors are faulty then the spare sectors will be used. Nice to see with newer hard disks and S.M.A.R.T. tools.
What you see as "Low Level" is nothing but a rewriting of the file system (Fat16 and FAt32 for most cameras). The normal in-camera formatting is a Quick Format where only the FAT is deleted, the card appears empty but the data itself are still present and untouched. That's the point where recovery tools come in and recover the data based on the information at other points in the file system.
If Low Level Format is Not checked, the card is 'formatted' in a flash.
if it IS selected, it takes some time to format the card
(I imagine, this is because the card actually Is formatted, not only that the FAT is deleted).
In the case of Low Level Format, recovery is likely impossible...
(best to check this out if you're planning to fork out money for software...
...maybe I should have bought a sandisk card with recovery software )
Wikipedia: Low Level Format
The term "Low Level Format" is often incorrectly used for either re -initiating a disk or creating an empty file system (which is the case here with memory cards). For FAT16 and FAT32 there are the mentioned two ways: a) Deleting the FAT and replacing with an empty one (Quick Format within 1..2 seconds; b) creating a new and empty file system (takes more time).
AFAIK, no. Unless you have access to forensic methods and tools. A new file system means that the former file system and all meta data of file organization are gone. Without this the content of file system clusters (if still existing) is meaningless.