For those who are not familiar with the term, horticulture is defined as the art or science of cultivating fruits, flowers, and vegetables (Webster's New Twentieth Century Dictionary, Unabridged). Horticulture is a composite science with strongest influence from plant physiology and pathology, botony, biology, chemistry, soil science, and genetics. Other sciences are involved, but the ones listed readily come to mind at this writing.
Bulbmeister.COM - Back in 2000, I created a site for exchanging information, including culture, images, and shared discussion, about flowering bulbs, especially spider lilies and rain lilies. The site has grown into a retail site making these available as well as other tender and hardy flower bulbs.
The Pacific Bulb Society (PBS) - An EXCELLENT resource for flower bulb enthusiasts to share ideas and view descriptions and images of their favorite varieties and species. Many folks share discussion online, and, if you are a member, they have an excellent and active seed and bulb exchange. They are a great group of enthusiasts with a lot of knowledge to share.
Dave's Garden - Are you looking for plants to add to your landscape, but you have reservations about ordering them online? Go to Dave's Garden to gain valuable information about companies rated by folks just like you. Dave also runs a very active forum community of gardening enthusiasts.