You can use a variety of materials to construct raised beds. Most beds are made of wood.
However, pavers make great edging material that lasts virtually forever, and this works great when edging up to a concrete path. A simple paver costs between 40 cents and $2 at Home Depot(depending on size). You will need about 30-60 pavers (depending on size) to build one raised garden bed. Here is a good example of such inexpensive paver: Pavestone Holland 4 in. x 8 in. Concrete Paver, 39 cents http://goo.gl/F2OEF
To get good alignment, get some chalk and draw a line across them to indicate how far you bury one end into the ground. You can also put a wooden stake at each end, and stretch a piece of string across the top at the right height to get the tops level if the ground is uneven and can’t be used as a reference. You can hang a small builders line level on the string to make sure your string sits level if you have one.
Pavers at Home Depot
How to Build a Raised Island Garden Bed with Retaining Wall Bricks:
Paverstone Landcaping & Garden Edging - DIY videos from Home Depot:
$35 raised bed at Home Depot
How to Make a Raised Garden Bed from Bricks - YouTube http://buff.ly/1f7U9AH
Raised Garden Beds « Deep Green Permaculture http://goo.gl/5o1qa
Raised Beds & Accessories - at The Home Depot http://goo.gl/aj5kE
Greenes 48 in. x 48 in. Cedar Raised Garden Bed, $34.97 at The Home Depot http://goo.gl/FtSK5
How to Build a DIY Raised Garden Bed - The Home Depot http://goo.gl/9nqyc
Pavers & Step Stones at The Home Depot http://goo.gl/bMmD0
Successful Raised Bed Garden - Cement Block Construction - YouTube http://goo.gl/4q34e
Home Depot Buying Guide: Pavers http://goo.gl/bPc2T
Raised bed with pavers - Minneapolis Square Foot Gardening Plan | My Square Foot Garden http://bit.ly/VklZML