Sprite Splitter is a Java program designed to take a SpriteSheet/Atlas (png/jpg/jpeg) and split them into separate images. I works on any sprite sheet, but since it was designed to split the console version of Minecraft's atlas, I feel it appropriate to post here.
By default it handles a 16x16 sprite, however you can change this using the arrows or entering an integer bigger than 0. If a image is loaded, it will updated the estimated sprite count automatically. If there are less then you can limit the amount created by checking limit and setting it accordingly.
To the sprite sheet simply click File >> Open and select the image. To choose the save destination clikc File >> Save To and choose the folder. Both will be displayed on the gui and are needed for the program to run.
By default it names each image as they are created in increments of 1. The next update will add custom naming from a file and can even be used to put them in separate folders.