Register is used to keep track of things like DVD movies, addresses, book collections etc. It is designed to be very simple and have a minimum of configuration.
Register organises the data as register documents of tables. Each row in the table (called "card") has some keys and values (eg "title" = "Solaris", "Region" = "2") that can be displayed in columns. Adding or deleting columns does not affect the data, but only controls what you view. Cards can be copied and pasted or dragged between different register documents regardless of which keys or columns that the different documents contains.
Tables can be loosely linked so that the selection of one table controls another table. This allows for simple relational databases.
Data can be imported from tabulated text and can be exported as html tables and tabulated text.
Register is free to download and use and runs on Mac OS X.