I have written a software in python with which you can catalogue electronic components in a simple way. The program is written on GTK and requires Python 2.6 with gtk module (if you have a Gnome desktop environment, there is a pretty good chance, you have these). If you don't have Linux, there may be a way to use this on Windows, I just haven't figured it out yet (there is both python and gtk for Windows, I just can't make it work).
The program has 7 categories: Transistors, Capacitors, Resistors, Diodes, ICs, Buttons/Switches and Other if something doesn't fit anywhere. You select a category by clicking on one of the appropriate buttons.
When you selected a category, if there are catalogued components in it, they will show up in the list. (When you first start the program, all of the categories are empty.) After this point, you can either add, remove or edit a component. Every registry has 4 attributes: a name (or type, like BD139), a quantity, a place (this can be anything like how you name the place, where it can be found) and description (this can contain some information about the piece, like Wattage for resistors, emmiter, collector, base order for transistors, or a "-" sign if you prefer nothing).
There are two handy buttons: an Inc and Dec button for simple and quick increase or decrease of the quantity of the selected component. You can sort the list either by name, quantity, place or description.
There is one restriction in the software. The largest quantity amount can be 99999, which I think is enough, for not anybody has a depository of electronic components.
I tested the software for pretty large entry numbers. It can handle with ease 10 thousand registries in a category, the only problem is when you try to delete all of them (or a pretty big amount), then you have to wait a few seconds.
I hope there are plenty Linux-users out there, who will find this little program useful.
Update on 18th December 2008:
I've added search capabilities into the software. You select a category, type in the term to search for and search away :D You can set to search either in name, description or place (or all three.. or just two... you've got the idea) and with the Match Case option you can search only for the exact matches (because it's case sensitive... obviously).
Step 1: Download
I publish it OpenSource, but you may not use it for any commercial purposes (I mean you may not sell the program, even if you edit but if you wish, you can use it in a shop... - wish it would be that handy :D)