PhaseOne is well-known for offering digital backs and software for Hasselblad and Mamiya cameras. The Danish company’s Capture One RAW processing software was designed for professional photographers. Though debatable, it’s still regarded as the best RAW converter by many pros and it is my favourite program, too.
Known for their sensor tests (see dxomarks.com) the French company offers a high quality RAW converter and image processing software, too. Especially the latest release of Photolabs is very good, IMO and may be an alternative to CaptureOne in some aspects, especially for architecture photography. Apart from the long approved lens and camera profiles and noise reduction, the use of AI for the tools in Photolabs is promising.

The company also offers the popular NiK Collection that includes an extensive set of very good filters and is used by many photographers me included

AV Stumpfl Reknown Austrian company producing high end show control, multidisplay, projection screens, touch control and audiovision equipment. I use their highly rated Wings Platinum software for my digital AV presentations. For their other products, use the Url http.//www.avstumpfl.com
Topaz offers tools for image noise reduction, sharpening, photo enlargements and more, – usable as stand alone programs and Photoshop Plugins. Based on Artificial Intelligence (AI) some of the tools can lead to significant improvements. I regularily use AI Denoise for editing and highly recommend it. Depending on the image content, AI Gigapixel can be useful for enlargements, too,-  i.e after cropping.
NatureScapes.net My most visited resource for nature photography, offering a very competent forum on digital and photography topics, excellent image galleries and much more.
Known and well-respected review site for DSLRs, MLs, lenses and accessoires. Especially the lens comparison tool is widely used to judge and compare the resolution, chromatic aberration of the optics
The Luminous Landscape Founded by the Canadian Photographer Michael Reichmann, the comprehensive site has been devoted to landscape and nature photography, featuring product reviews, tutorials, photographic techniques and more. It has been one of my favorite sources of informations before. After Reichmann has passed away some years ago, the site has been redesigned and become a membership site. So I haven’t visited the site anymore since they’ re charging for the access to most contents, now. The informative forum still is accessible to date, though (read only)
fredmiranda.com Fred Miranda’s site has very informative forums covering all kinds of photo gear, photographic topics and also boards for image presentation and critics. It offers equipment reviews and feedbacks from users, too. Fred’s Buy & Sell board for used gear is a known and respected address for registered users, but probably an attractive option only for photographers living in the US.
imaging resource Run by Dave Etchells, the site posts latest news on digital cameras and film scanners. It offers excellent digicam reviews including an instructive “Comparator” for digital camera image comparisons.
Neat Image Neatimage is a widely known tool designed to reduce visible noise and grain in photographic images, produced by digital cameras and scanners. The software can be used as a Photoshop plugin or standalone application. Though today’s DSLRs produce pretty clean files within a wide ISO range, I sometimes used the program for accurate noise reduction in high ISO images or long exposured photographs – such as Northern light shots. it’s a good and effective tool, but I preferably use Topaz  AI Denoise now and have not tried the latest version of Neatimage yet..
dpreview.com Established in 1998 by Phil Askey, Digital Photography Review probably is the largest and most visited website on digital photographic topics, primarily covering detailed reviews/previews of digicams and many discussion forums.
dforum.de German based information board and discussion forum for Canon photographers. Everything on this site is in German.
birdsasart.com Website of the renowned bird photographer Art Morris featuring photos, books, instructional photo tours and sharing Morris’ thoughts on lenses, cameras and accessoires.
epp PTLens is a software that corrects lens pincushion/barrel distortion, vignetting, chromatic aberration, and perspective. For correcting CA, I oftenly prefer the program to the similar Photoshop filter.