Brick is a common landscape edging choice: It's classic, widely available, and relatively inexpensive. Push bricks tightly together to minimize spaces between them that turf can slip through. To prevent heaving and unevenness, set your bricks in a bed of sand.
Note: If you set the brick just above the soil, you can use it as a mowing strip, running your lawn mower's wheel right over the brick. This eliminates the need for trimming.