Go to admin/build/imagecache and define the following presets:

  • Preset Namespace: “large”
    • Action: “Scale”, width: “600”, height: empty, upscale: no
  • Preset Namespace: “small”
    • Action: “Scale”, width: “100”, height: empty, upscale: yes
  • Preset Namespace: “small_quadrat”
    • Action: “Scale”, width: “150”, height: “150”, upscale: no
    • Action: “Crop”, width: “100”, height: “100”, xoffset: “center”, yoffset: “center”
    • Action: “Resize”, width: “100”, height: “100”

You can alter the values as needed, but for “small_quadrat” you should use this name and a final size of 100x100. All values in pixels, not %!