That is, it used to be called that and is still available in Ubuntu under this name (sudo apt-get install qtpfsgui). However, qtpfsgui is discontinued since mid 2009 and has been replaced by the Luminance HDR project.

Since qtpfsgui crashes under ubuntu 9.10 when attempting to save any HDR image, I downloaded the latest luminance version, compiled and installed it like so:

1. Download the luminance source and unpack the folder.
2. Install the dependencies required to compile luminance:
   sudo apt-get install qt4-qmake libexiv2-dev libopenexr-dev fftw3-dev libtiff4-dev libqt4-dev g++ libgsl0-dev
3. Compile luminance (takes a few minues) and install it. Change to the unpacked luminance folder and do:
   qmake
make
sudo make install

That´s it! you now have luminance installed and it should be in your main menu under applications>graphics.

It works perfectly with Karmic.
One of the best things about luminance is that you can play a lot with the algorithms and parameters used to tonemap the HDR into a LDR image. In contrast to many other (commercial) tools, you actually get to know which algorithms are used, who created them and can read a little more on how they work (if you are not to opposed to mathematics) by googling up the corresponding papers.