National Garden Clubs, Inc
Local Garden Clubs
Native Plant Publications available from the PennState College of Agricultural Sciences - select the Search option and type in Native (or whatever type of publication for which you are looking).
PlantCare.com is a database of over 1,300 species of House and Greenhouse Plants which provides 18 categories of care from watering to lighting. Search by name, plant type, shrub, fern or perennial.
Western PA Wildflowers Bob Zuberbuhler of Beaver Falls has put up what is essentially a field guide to native wildflowers on his website.
Weekend Gardner is a web magazine with lots of tips and suggestions.
Garden Designers Roundtable is ablog that includes 21 professional landscape and garden designers from all across the United States and Great Britain. They explore and discuss the world of garden design.