The components of the Huygens Suite (like Huygens Essential) have many free functionalities when used without a License String. You can use them for example to read and convert between many File Formats, (as ICS or Tiff files), or to view 3D stacks with the Twin Slicer. Some of the freeware functionalities are:
Image read/write in many File Formats (a few special ones require a license)