The site is a promo for their subscription service, but it does provide a variety of services for the casual browser. It covers all states and some foreign countries. If you know of a place they've missed, they invite submissions. Covers ornamentals, landscaping, weekend gardening, etc. This site's an award winner.
Emphasis is on sources for temperate to cold temperate zones.
Has sections on herbs, bonsai and lawns and soils. An attractive site that offers sections on wild-flowers, tours of botanical gardens, gardening puzzles, a seed exchange, and a directory of online gardening vendors. Another award winner with tips and advice as well as an online garden shop. This can help if the area you have an interest has a multitude of sites and you don't want to surf aimlessly.