Some of these you'll find useful to spiff up your photos, others you can use to create graphic designs from scratch. Most of the brushes come with no limitations but some are restricted to non-commercial use only - read the descriptions carefully.
To install the brushes copy files with .abr extension from zip archives into this folder: Program Files > Adobe > Photoshop (xx) > Presets > Brushes.
Here are some links that I think may be useful for those of you who are just starting with photography (or thinking about it), as well as for more seasoned photographers. No matter how long you have been doing it there is always something new to learn.
http://www.betterphoto.com/allAbout.asp - this is a very good place to start if you are new to photography
http://luminous-landscape.com/ - tons of techniques and tutorials, hardware reviews, etc.
http://scantips.com/ - must know for anyone dealing with digital images. Very comprehensive explanation of resolution.
http://computer-darkroom.com/ - Adobe Photoshop and Lightroom tutorials, printing tips, color management
http://retouchpro.com/tutorials/index.php - extensive collection of Photoshop tutorials on retouching.
http://www.russellbrown.com/tips_tech.html - scripts and tutorials from Photoshop guru Mr. Russell Brown.
http://www.ronbigelow.com/articles/articles.htm - very good collection of articles generally targeted for more advanced hobbyists.
http://planetneil.com/tangents/flash-photography-techniques/ - learn how to use your flash.
http://strobist.blogspot.com/ - lighting with off-camera flash. Brilliant! You need to understand photography basics before coming here.
http://photoserge.com/ - great collection of Adobe Photoshop and Lightroom tutorials by French photographer Serge Ramelli