Image Cutter is an useful app that will let you cut an image automatically exporting all the parts in separate files and with the relative HTML.
Just select the places where to cut and click on Export and you're done!
As simple as that!

Main features:
√ Simple, beatiful and intuitive UI
√ Cut the image automatically in columns or rows evenly spaced
√ Drag the handles to move the split lines
√ Change the line color
√ Pixel perfect cuts
√ Smart rulers to show you how many pixels you're cutting
√ Export the images and an HTML page with the code ready to be used