There are a scads of organizations, retailers, software manufacturers, online services, labs, and resources available to digital sports photographers, whether you want to go pro or just go out and shoot a backlot stickball game. Here are some I think are noteworthy and/or interesting to help get you started:
ACD Systems: Software manufacturer of ACDSee and other applications.
www.acdsystems.com
Adobe: Software manufacturer of Photoshop and Photoshop Elements.
www.adobe.com
Adorama: Major photography retailer.
www.adorama.com
American Society of Media Photographers: Professional society for photojournalists.
www.asmp.org
B&H Photo: Major photography retailer.
www.bhphoto.com
Express Digital: Software manufacturer of products for professional and amateur photographers such as Digital Darkroom.
www.expressdigital.com
Graphic Authority: Electronic educational tools and tutorials for photography.
www.graphicauthority.com
IAPEP-International Association of Professional Event Photographers: Highly oriented to sports photographers as well as general event shooters.
www.iapep.com
Kodak EasyShare Gallery: Kodak's online photography lab, formerly called Ofoto.
www.kodakgallery.com
MorePhotos: Professional online photography fulfillment service.
www.morephotos.com
National Press Photographers Association: National organization for photojournalism, including sports photographers.
www.nppa.org
Photo net: Huge online photography community.
www.photo.net
Photodex: Software manufacturer of slideshow software such as ProShow and ProShow Gold.
www.photodex.com
Photographic Society of America: Worldwide, interactive photography organization for all types of photographers.
www.psa-photo.org
Photography-on-the.net: Forums and information, all about digital photography.
http://photography-on-the.net
PhotoLinks: Online photography directory.
www.photolinks.com
PhotoReflect: Professional online photography services.
www.photoreflect.com
Printroom com: Professional online photography services with many sports and event photographers.
www.printroom.com
Professional Photographers of America: Professional society of photographers.
www.ppa.com
Shutterfly: Online photography lab.
www.shutterfly.com
SportsShooter com: Online community and resource for sports photographers and other working photojournalists.
www.sportsshooter.com
The Nikon Users Community: User group discussing all aspects of shooting Nikon cameras.
www.nikonians.org
Yahoo! Photography Groups: Many informative groups about all aspects of photography. Search for photography, digital photography, or sports photography.
http://groups.yahoo.com