If you are referring to the plant in the foreground, this appears to be a type of sedum or stonecrop plant. Once the blooms are complete, it may be easer to identify the specific variety by the color. There are many varieties of sedum from low growing ground cover to taller plants. Many provide wonderful blooms in late August and September.
The Missouri Botanical Gardens has information on many varieties at - http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderListResults.aspx?gen=Sedum