After trying out a number of Linux photo-management applications, I have settled on Digikam. It has some great tools for managing vast photo archives, wonderful RAW support, and an array of good photo-editing-and-fixing features. Two introductory articles are on Linux Planet:
Digital Photo Management In Linux, Part 1
Digital Photo Management In Linux, Part 2
Not mentioned in the articles are Digikam’s Plugins, which extend its usefulness considerably. Such as Noise Reduction, Refocus for rescuing blurry pictures, BlowUp for good-quality enlargements, white balance adjustment, and many more.
Over on LXer.com you might find some useful information on photography fundamentals, such as lens types and quality, and understanding how to use aperture to make your photos say what you want them to:
Adventures in Digital Photography With Linux, part 4: Fundamentals