Collectors of business cards can build massive collections. Once collected, it is important to store them in an appropriate way. Most collectors treat the more valuable items in a different way to the less valuable ones, for obvious reasons.
Storing valuable Business Cards.
Valuable business cards are probably calling cards or trade cards. These cards were produced between the 17th and 19th centuries, and are quite rare. Collectors often wish to "show off" their best items. For this reason, books with plastic slots made to the size of business cards, have been used for storing and displaying the cards. Make sure that the sheets are make from archival type material, otherwise they can damage the cards. These are available as loose leaf files or fixed spine books, from good hobby and craft shops. They are also available online. Some collectors use photo albums for the odd sized cards, particularly the very early cards which are slightly smaller then modern playing cards.
Storing Bulk Business Cards.
Collectors tend to use either small plastic zip-lock plastic bags which can be purchased from stationery and printing retailers with hard plastic containers with or without partitioning or simply boxes that are designed to hold large numbers of business cards. The optimum sized zip-lock bags store approximately fifty business cards in a small reasonably tight bundle. Be sure to label these and enter the details into the cataloging system.
The small zip-lock bags can then be stored in the plastic containers to ensure that they remain dry and out of the sun. Some collectors use a system that removes the air from the bags as part of their process. It is a good idea, especially if you are bundling during times of high humidity and because paper is hygroscopic (it absorbs moisture from the atmosphere). It is probably best to package the cards when the humidity is low to avoid any of the potential consequences. Business card storage boxes can be obtained from good hobby and craft stores and online.
Develop you own procedure for storing (and numbering for cataloging) so that you collection is truly unique and serves the needs that you desire. Above all, build your collection with fun and you will meet interesting people and finish up with a collection that is worth something, both to yourself and others.