I have a folder in my computer for each quilt I've made, along with the pattern and any progress shots or whatever.
I also have a plastic 9x12 envelope for each quilt and in there I keep all my notes - calculations, design ideas, pattern stuff, and a copy of the pattern if I had one. That way I can look up what I did if I have to figure it out again.
Every quilt I've given away has a single page in a scrapbook called 'My Quilt Book' with the date made and the name of the recipient and a couple photos of the quilt. Of course I made my first one in January 2011 and I only have 14 pictures in the book to show for those three years!
Any leftover fabric goes into a clear plastic bag left open at the top and put into a drawer. The original pattern goes back into the looseleaf notebook which has all the patterns I have ever bought or cut out of magazine or whatever.
Am I a little obsessive? Probably, but my forgetter is working faster than my sewing machine!