After each quilt is done I take a picture of it, and, if it is made for someone specific I like to also have a picture of it with that person.
I do have a beautiful (about 10x7") spiral notebook with a double page (facing each other) in which I put the thread color numbers and for what each was used, and stitch # for each different type of stitch. Let me tell you, I refer to it again and again. I'm not a "block" quilter, but do more or less original designs, and having the exact stitch (along with it's width and length) and the exact thread noted saves me all sorts of time!
My pictures are on my computer and on dvds, but I want to have printed copies put into my notebook also. Since I am basically "self-taught" I found myself "reinventing the wheel" too often and it is great to be able to go back and see what worked before for a specific effect.
Disclosure: I am NOT a "neat" quilter, my quilts aren't perfectly squared, my stitching isn't straight... etc. I simply cannot use patterns, both because I have a terrible time trying to figure them out and I HATE repetiton. Most of my quilts have been made for specific people, and even those which will be going to someone who needs the love or comfort I imagine the person and quilt my best for that image. Most of my quilts are OK, a few have been great (I know because, while I never will win a judged award, I have won "viewers' choice" a few times).