These are all things I actually use, typically as core components of my digital darkroom. I only recommend from experience. I have no financial interest in any of these items -- I haven't been paid by or received any benefits from any company related to these products. I'm simply a satisfied customer.
DDI Software is run by photographer and developer
Mike Chaney, maker of several software tools. The indispensable one for me is
Qimage. You can think of it as a Swiss Army knife for photo printing. Reasonably priced yet packed with functionality that rivals software costing hundreds of dollars more, one of Qimage's key design themes is premium quality output with powerful layout options and efficient workflow. All of my own photo prints are made with Qimage, and prints that I have prepared by third-party services are often prepped through Qimage before I send out the master files.
HDRsoft, a French software company, are the makers of
Photomatix Pro. Photomatix is one of the most popular High Dynamic Range (HDR) processing tools out there. On the market since 2003, it's also one of the longest shipping HDR tools. I have been using it since 2005, and have found it to be a powerful and indispensable element of my digital toolbox. I wrote extensively about Photomatix in my HDR article linked above, and still use it heavily today. Many of my images shown on this site and elsewhere were created in part with Photomatix.
Imatest is a company founded by master photographer and pioneering digital imaging scientist
Norman Koren. He produces the software tool of the same name, but what I'm linking to here is his other main tool
Gamutvision. Gamutvision is an incredibly useful piece of software that lets you slice and dice ICC profiles, whether for monitors, printers or other devices, and compare them to each other using a wide selection of metrics and visualization techniques. Quite simply, applying Gamutvision to color management in my digital work was a tremendously enlightening experience. If you work with ICC profiles in a color managed workflow, this tool will give you a nearly unrivaled depth of insight into what is going on with your images as they pass through the color management system. It's worth the learning curve if you care about color.
Kolor, another French software company, has produced
Autopano Pro since 2005, now joined by Autopano Giga since 2009. Based in part on technology licensed from the University of British Columbia in Vancouver, B.C., Canada, Autopano is a sophisticated yet easy to use stitching tool. Digital stitching is another staple process in my digital darkroom, whether to create large format panoramic images, or densely detailed images in a traditional aspect ratio like 4x5. Autopano handles many complex situations, including gigapixel scale stitching jobs, and it natively supports HDR projects. It's another indispensable element in my work.