Archives:

New York City Department of Records - Photo Gallery - the largest collection of historical images of New York City in the world
Gateway to Astronaut Photography of Earth - NASA

Digital Photography:

Digital Photography Review - News, Reviews, Forums, FAQ
The Imaging Resource! - Digital Cameras, Digital Camera Reviews
Camera Career - A 216-Page Guide to Selling Your Photos
Vandelay Design Blog - 33 Marketplaces to Buy and Sell Stock Photos and Graphics
Shutterstock - Stock Photos and Royalty-Free Images by Subscription
diglloyd - Blog
Camera Manual Library - free camera instruction manuals, camera instructions
Flash and Light Meter - instruction manuals

Digital Cinematography:

ARRI Channel on Vimeo
ARRI Group: Pro Camera Accessories
Scoop.it - Digital Cinema Tools

Learning:

Strobist - resource for photographers who want how to learn to use their flashes like a pro
Anleitung fürs entfesselte Blitzen
Strobist-Hardware-FAQ
Den Umgang mit Licht lernen - Strobist - Lighting 102
The Photo Brigade - Workflow
Anwendung von Farbmanagement in Adobe Photoshop - Farbeinstellungen, ICC-Profile, Rendering Intents, Proof
Technik-Tutorial
Tutorial Elektronische Bildbearbeitung
Bildgestaltung
Stanford Computer Graphics Laboratory - CS 178 - Digital Photography (Spring 2014)
Nine Degrees Below Photography - color management & photography using free/libre software
www.erik-krause.de - Verzeichnung und Farbfehler korrigieren mit PanoTools und PTGui
www.erik-krause.de - Determination of chromatic aberration correction parameters
U Contrast Masking - Luminous Landscape
Manual Focusing - ZEISS International

Legal:

Panoramafreiheit - Wikipedia
Bildrechte - Wikipedia
Wikipedia: Bildrechte

Software:

Prof. Dr. H. Dersch - HFU Furtwangen - homepage of Panorama Tools, free software for authoring and displaying virtual reality panoramas
Fix Corrupted Nikon D4/D600/D800/D800E NEF Images
darktable - the photo workflow software
ShiftN - automatic correction of converging lines
MV's Plugins Perspective Transformations - lets you carry out both active ("Modify") and passive ("Rectify") transformations
MV's Plugins Contrast Mask - enhances images with too much contrast by applying a technique known as contrast masking
MV's Plugins Wire Worm - remove wires and other unwanted objects from your images
MV's Plugins Vignette Corrector - correct the brighness fallof at the corners of an image
The Plugin Site - Plugins for Photoshop, Lightroom, Elements, Paint Shop Pro, Corel, After Effects, Premiere and more

Technology:

Photo Strobe Trigger Voltages - is your old strobe safe to use on your new camera?
Markus Keinaths Photohomepage - Foto Selbstbau
Markus Keinath's Photohomepage - Photographic camera DIY repair and modification
Guide to Photo Metadata Fields - photometadata.org