How did the photos get on the iPad e.g. taken with the iPad or synced from a computer ? For photos taken with the iPad, copied to it via the camera connection kit, or saved from emails/websites then see this page e.g. on a Mac you can use iPhoto, Aperture or Image Capture
For photos that were originally synced from a computer you will need a third-party app such as Simple Transfer which can copy them off via your wifi network. But as photos are 'optimised' when they are synced to the iPad, any that you then copy back to a computer may not be exactly the same as they originally were on your computer.