PrintFile pages for both the negatives and the contact sheets. I use looseleaf binders from Light Impressions, they are archival and oversized, so that the PrintFile pages do not stick out. I "interleaf" the contact sheets with the negatives, so when you look at a contact sheet, the "facing page" is always the negatives for that sheet. The binders go on normal shelves in my library, a better environment than my basement darkroom. Since I shoot 35mm, medium format, and large format, one advantage is that I can keep all formats and the related contact sheets intermingled in a looseleaf, so the organization is chronological, not by format.