Tips and lessons
• The National Press Photographers Association is considered the leading organization for photojournalists, offering training in skills as well as legal rights and other relevant subjects. As the name suggests, much of this content is advanced and pertains mainly to photojournalists, not art photographers or advertising photography (though many of the same principles apply).
• The Poynter Institute is a leading school for journalists with a vast website full of lessons and news for journalists. Much of the site focuses on print journalism, but this is the visual journalism section, with extensive information about photojournalism.
• Photo Techniques Magazine has a site with beautiful photos and useful tips. Again, this is pretty advanced stuff, but it is more skewed toward art and nature photography rather than photojournalism.
• The Kodak site has a broader range of information. The company obviously wants folks to buy and use its cameras, printers and accessories, so it's going to teach you how to keep improving your photography. It has lots of good information for beginners with basic cameras, but I don't recommend the site for more advanced photographers.