Back when I was a serious garage/estate sale shopper, when I had more space, I always looked for those spiral-bound regional/church/sorority fund-raising recipe books that someone already mentioned. They accumulated pretty fast and I had a lot of them - they were fun and interesting reading, partly because of the various names given to the same set of ingredients. But I seldom used recipes from them and have since donated most of them. I still have my Joy of Cooking from the 60's and refer to it for methods occasionally and can't imagine not having it. Most of the other regulation paperback cookbooks (like "Fresh Fish" and that sort of thing) haven't been touched in a long time. Guess I should donate them, too, since I tend to use the easier, faster 'Net for day to day searches. I've copied & pasted (and used) a bunch of good-sounding DC recipes onto Word docs.
Technically Not Cookbooks department:
All those old newspaper clippings that I go through mostly around Christmas time - I really should toss them - some of them are from the 80's and I haven't tried them yet. I guess part of that is sentimental since they're from lots of different places - St. Louis Gooey Butter Cake, for example.
Also, I like to try dishes from the light fiction mysteries that have recipes incorporated in them - those make a round trip to/from the library, but they're "my cookbooks" for 3 weeks.