You can save some real time if you come across Mail messages on iPhone or iPad that have multiple images you want to keep around.
To save multiple images at once from a Mail message to Cameral Roll in Photos, tap the Reply button. One of your options will be “Save [X] Images.” This saves you a lot of tapping, as it sends all images to the Camera Roll with a single tap.
In my testing, this only seems to work with images. I couldn’t get it to work with non-images, such as a message containing multiple Pages documents.