StauffKeeper - versatile, nuanced and capable, but a serious time investment
Designed to be so versatile that it can catalogue just about everything under the sun, StuffKeeper meets that goal with aplomb. Which is impressive, considering it's still awaiting its first stable release.
However, this is a Marmite program, and what we love, you may hate. Contrary to most collection managers that provide pre-built templates with a horde of defined fields, StuffKeeper requires you to set up the collection fields yourself.
This may seem like a handicap, but the result is a cleaner collection that isn't burdened by empty fields. Plus, you'll be able to enter items quickly, because you'll have a better grasp of what data you'll need.
You can create as many fields as you like for each collection, but note that the interface is fairly basic and requires some getting used to. And while there's a basic tour to help you get acquainted with StuffKeeper on its website, the lack of detailed documentation makes this program ideal only if you're willing to devote plenty of time and energy to it.
To help you sort through your entered data, you can create tags for items in your various collections and search using these tags just by typing them into the search bar. Additionally, you can search for data entered in any of the fields for your collection and, best of all, you don't have to be exact.
For instance, you can search for all Liam Neeson movies in your collection by typing Liam in the search bar, which looks for that keyword in text fields as well as any related tags. Finally, it's worth noting that StuffKeeper creates a database for each of the collections and enables you to back up all your stored data in compressed tarballs.
Licence: Free under GPL
The tags are great, but having to create fields is sure to divide opinion.