Any place old things are stored is worth rummaging through. But collectors are a fussy bunch, so keep in mind that condition is an important factor in fixing value. But old coins don't have to be gold or silver to have substantial value. If your grandmother saved things, you may find an old copy of an early catalog which could be worth some money. If you're planning to do renovations to an old house, break down the walls carefully.
Collectors avidly buy old scrapbooks, the older the better.
Scrapbooks containing postcards, advertising card, newspaper and magazine clippings always bring good prices. Again, the older, and rarer, the better. Joseph Luft's Philatelic Resources on the Web is an annotated directory of Web resources of interest to stamp and coin collectors. You may find an old copy of the original Action Comics Superman, a very highly valued item. It includes articles on how to collect comic art, where and how to find it and why you should want to collect comic art in the first place.