Establish a clear boundary line between the yard and the street. A rustic rail-style fence works well for this, with one 4- to 8-foot section meeting another at a right angle. Some homeowners put a large rock at the very corner, which definitely keeps the cars from cutting too close.
Extend hedges from the corner down both sides of the yard. Bushes such as forsythia are fast-growing and will provide bright yellow flowers to start the spring. They can be left to grow tall if you prefer privacy or you can keep them trimmed to a preferred height.
Plant junipers along both sides of the corner for both privacy and sound control. This dense evergreen grows to about 12 feet in height and effectively screens out everything on the other side.
Develop a sun-tolerant garden on the corner. Many corners are exposed to full sun and require plants such as Russian sage, coneflowers, lavender and Shasta daisies. These plants are also tolerant of drought and do not require as much watering.