This is a great DIY project if you're looking to spruce up the living room. Measure up your current cushions, buy some fabric you like, a few zips (just a little shorter than the full width of your cushion), a reel of matching thread, and you're good to go.
This is the old cushion I was measuring up and giving a face-lift.
Cut around your old cushion cover, leaving about 15mm space on all sides as seam allowance. Should you be into accuracy, you can of course just draw out a square including seam allowance with fabric chalk.
Measure how much space to leave on either side of the zip. In my case, I left 5cm on either side
Put the right sides of your fabric together, and on one edge of the fabric, mark where your zip will go. Starting at one end, stitch up to the zip marking and backstitch. Now stitch up the zip opening, but with a nice big stitch, so you can easily unpick it later. When you reach your net zip marking, backstitch, and sew up properly to the end. Press your seam open on the inside.
Lay your zip face down on the wrong side of the fabric between the two marked openings, and pin into place, making sure that you can feel the teeth lying along the temporary seam.
Using your zip foot, sew down the right side of the zip, across the bottom, and up the left hand side. Open the zip. Now pin the other three edges together and stitch closed. I also overlocked the inside edges after I had sewn them, as extra reinforcement.
Et voilà! New DIY cushion covers! I trotted out four of these after dinner, and one morning before work. It's do-able! Give it a go, and have fun!