Maryland Outfitters and Guides Association Inc.
- A non-profit business trade association representing the interests of Maryland Outfitters and Guides. Includes bylaws, code of ethics, and members.
- http://mdoga.org/

Maryland Geocaching Society
- Geocaching related resources related to caching activities in Maryland. Site includes forums, chat, cache listings and coming events
- http://www.mdgps.org/

Maryland Artifact Recovery Society (MARS)
- Metal detecting club. Site offers a newsletter, photos, applicable state park regulations, classifieds, and object identification requests.
- http://marylandartifactrecoverysociety.org/

Maryland Watermen's Association
- Focuses on the interests of all who derive beauty and benefit from the waters of the Chesapeake Bay. Features overview of events, programs and services, special interest groups, and contact details.
- http://www.marylandwatermen.com/

Maryland Outdoors
- Directory of Maryland-based resources for outdoor recreation activities.
- http://www.unitedstatesoutdoors.com/md/

Maryland Outdoor Club
- Free club promoting adventure sports, travel, and social activities statewide. Includes club background, upcoming events, membership information, and area happenings.
- http://www.marylandoutdoorclub.org/

Maryland Outdoor Group
- Yahoo group for 20- and 30-somethings in the central Maryland/northern Virginia/Washington D.C. area. Fir those interested in hiking, camping, backpacking, climbing, spelunking, walking, traveling, and sight-seeing.
- http://groups.yahoo.com/group/MDOutdoorGroup