For big projects, each one gets a separate folder on the computer to keep track of progress, for the rest, I always take pics of the fabrics I'm going to use and then pics of the top and pics of the finish.
Just recently I made a hard cover coffee table book of my quilts using Photobook when they had an 80% off sale and it turned out really nice and is a great way to keep a record of all the quilts I've ever made (That I have pictures of.) It was easy to do on line and shipped really quickly and I think with shipping I paid less than $35.00 all in (CDN)
Watson