If you spend a lot of time Googling plants, you have probably already come across the Dave's Garden website. If you haven't, it is well worth a visit. The website is an incredible resource for information and images about an astounding number of plants. I use it to go one step beyond the Sunset Western Garden Book.
Dave's Garden is built by its users, so the information you'll find there has been entered in by other plant and garden enthusiasts. Because of that, there is a wealth of information on it.
In fact, it is so all encompassing, it can be quite hard to navigate. Instead of trying to find your way around on the site, try doing a Google search for a plant and add the word "daves" after the plant name. The first page to come up will probably be the Daves Garden PlantFiles page for that plant. The image above of one of my favorite grasses, Calamagrostis 'Overdam', is pulled from its PlantFile.
The PlantFile will typically have many images of the plant, a section of basic information such as plant height, and a very useful section called Gardener's Notes. Here, gardeners have entered in their own experience with the plant (and you can see the city they live in to know if their observations might be true for you, too). Read these notes! They tell you wonderful things like whether the plant is invasive, if it is easy to grow, or if it needs to be cut back in the winter. In the Gardener's Notes, one gardener calls Calamogrostis 'Overdam', "a great upright grass that does not fall apart," and another notes, "As with most grasses, looks great with backlighting of a.m. or p.m. sun. Flower heads move in the slightest wind." Now that is good information.