About two years ago, I ran across the GardenWeb, and was very impressed. If you are the least bit interested in gardening, using the word in its widest possible sense, you really should check out this site.
The forums are lively. When some nice person posted about my website, the traffic to my site increased by ten times! If you have questions (or answers!) about gardening, garden design, garden art, check out the GardenWeb.