HDR Images with free software
Those cool, fancy images are all over the Internet. Many people call them HDRI (High Dynamic Range Images), although they usually are not, at least not originally. HDRI cannot be displayed by current hardware, and also not be taken by most cameras. Thus, most pictures start out as LDR (Low Dynamic Range) images and are enhanced to HDR images through DRI (Dynamic Range Increase).
Creating true HDR images of course is possible with a 3D-program like Blender. You can easily render your scene in a HDR-format like for example OpenEXR and thus get a true HDR image.
In order to get your photos converted to HDRI you need to have exposure series, which usually consist of three images with different exposure (under-exposed, over-exposed and with the desired exposure). Modern cameras, like for example my Samsung NV10, offer a function for this.
By the way, the series is not limited to three pictures, it can be more images too, and sometimes I guess this might be useful.
After taking a series of images these have to be combined. As Gimp cannot handle HDR images it cannot be used for this. Gimp's fork CinePaint on the other hand is not only capable of handling HDRI but also offers an option to combine a series of LDR images to one HDR image.
As an HDRI, as mentioned, cannot be properly displayed or printed it has to be converted back to an LDRI for this purpose. This is done through tone-mapping. Qtpfsgui is a good tool for this. It offers different algorithms to reduce the HDRI to an LDRI which produce different results.
Many of those fancy pics on the net, have a somehow surreal look about them. This also is the result of the tone-mapping, and can be achieved with Qtpfsgui. But of course you can also tone-map the HDRI to a more real looking LDRI.
By the way, although also Qtpfsgui offers the function to combine a series of LDR images into one HDR image it seems that CinePaint does that job better. For tone-mapping then Qtpfsgui is the weapon of choice, so it is a good idea to have both tools on your system.