I have not made one, but I've been looking into it. My daughter is almost 18 months old now and I've been saving her oneies and special outfits to make a quilt.
I can't sew, wish I could, so I've been checking out places that you can send the clothes to and then they do the rest. Some are really expensive ($400 and up, yikes!).
I have found this site and it is really reasonable. You can either buy a kit containing everything needed to make a quilt from baby clothes - alternating squares in minky fabric, batting, a quilt back, safety pins, straight pins, a cutting template, and very specific directions. It costs $35.
Or you have the option of sending the quilt kit back with squares from the baby clothes you've cut, and they'll sew the quilt for you. That costs $75 and the site says it will take 3-4 weeks. Not bad in my opinion so that will be the route I take.
Here's the site: http://www.ticcheandbea.com/baby-clothes-quilts-s/1.htm