Below you will find web sites and other resources that I find useful. If there is one that you think I should add, please feel free to drop me a line and I'll check it out!
Aquatic Gardeners Association: This is an international group for people who enjoy working with planted tanks and aquatic plants. Please consider joining our group. It is not expensive, and member benefits include a beautiful, quarterly, full color magazine full of articles that you will not find elsewhere. There is also a member's only section of the website, where you can access videos of many speakers from past conventions and other special content.
Aquatic Gardeners Association Face Book Page: We have over 9,000 members on the AGA Face Book page, and whether you are a paid member or not, you are welcome to join us. Ask questions, share your knowledge or share photos of your tanks and plants!
Flowgrow: This is a German website, but can be accessed in English as well. It has the most complete and most accurate on-line information on aquarium plant species that I know of.
Aquatic Plant Central: For those who like forums rather than Face Book, this is a nice, smallish forum with knowledgeable people.
The Barr Report: There is a tremendous amount of useful information on this site, and it has always been carefully moderated. There are some areas of the forum that are subscription/fee based, but other parts are free and open to the public.
UK Aquatic Plants Society: Although this is a UK based club, the website is full of useful information as well as a very nice forum.
Green Leaf Aquarium: There are other on line sources of equipment for planted aquariums, but Green Leaf is great for one-stop-shopping for CO2 equipment, tools and fertilizers. Lots of good information and greta customer service too.
Greater Washington Aquatic Plants Association: GWAPA is a local group, but they have a tremendous knowledge base. They hold monthly meetings, but even if you aren't local, their web site has some very useful articles, and a well managed forum.