Cataloging a collection of minerals, fossils and meteorites
Even very interesting specimens are of little value without proper documentation. In the beginning of my collection, I usually just noted down each specimen's name and location where it was found on a post-it-note-sized piece of paper which accompanied the sample on the shelf where it was stored.
Soon, this system became lacking and I moved to assigning each sample a unique number. A small sticker with the number is attached to the specimen (with the exception of those, whose surface could be damaged or made less attractive by the label) while an index of descriptions corresponding to each number is stored separately. At first, this was a table in a notebook, but after some time I entered all the data in a computer spreadsheet. This used to be Lotus 1-2-3 at first, then Microsoft Works and now OpenOffice.org Calc. I have never seriously considered using a relational database for keeping track of my collection, even though it would probably be necessary if it were larger. Currently, it is at over 1000 specimens and the spreadsheet approach seems to still work quite well (and it is much easier to maintain than a DB would be).
Over the course of time, the amount of information stored for each specimen has increased. Early versions of my spreadsheet stored only each sample's number, name and location. Later, a field for the date was added and an extra field for remarks followed soon. My current system has additional fields for references (books and other materials helpful in identifying the specimen) and some extra records which help find a specimen on its shelf easily, along with a history of previous storage locations.
The field for remarks is used for all sorts of information which doesn't fit any other category well and is not common enough to become a separate field. If the system used a relational database, adding new fields would not be a problem and would significantly improve the DB's normalization. However, when a spreadsheet is used, having too many fields is unconvenient — so the remarks are a single field which in most cases contains human-readable text (which is hard to query for the computer if anything more complicated than a literal text or regular expression search is required). This field is used e.g. to store information about specimens bought at mineral and meteorite fairs (fair date and location, name and address of the dealer etc.). For meteorites, it is also used to store the specimen's mass and information related to the fall. Actually, meteorites could be stored in a separate spreadsheet with slightly different fields than those required for minerals and fossils. However, they are still much less numerous than minerals, fossils and rocks in my collection so making an exception for them is less trouble than splitting the catalogue into two separate indexes.