I wish I would have kept a journal/record.
I like the idea of using envelopes. That way you could have as much or little info in them.
What I would do - I think 6x9.5 envelopes are a fairly "common" size - One could have them printed with basic info on them - (I had trip envelopes made up for my husband for while he was an over-the-road truck driver. It had info on it such as date out - date back - destination - a section for fuel costs (gallons and cost, and other expenses - then all the receipts were placed inside the envelope.)
I think that could be adapted for a made item -
Name of item - maybe even have a photo on the outside of the envelope?
What happened to it - (given as a gift, kept, whatever)
Date started
Date finished
Photos
Inside the envelope:
Receipts
Either a sheet of paper or index cards with miscellaneious info on it.
You might also include what else was going on at the time you were working on it - personal, community, or world news.
Samples of fabric and batting.
I think one could use two layers of tape on one edge and punch holes in it so it could be put in a binder.