I simply use an Excel spreadsheet, and keep it in my Dropbox so I know what's in my lab wherever I go. I've created categories by simply keeping the sheets' names indicative of what's on it, e.g. Capacitors, Transistors, Resistors, and so on. I freeze the top line, which I use for part number, location, vendor, manufacturer, important nominal values like resistance or capacitance, and just keep adding any information that might help me find what I need in the future. Of course, you can use filters and the search functions, and organize by rows or columns. With a spreadsheet, your imagination is the only limit, regarding the types of data you want to store, be able to search, etc. You can even put in links to the parts' data sheets, and if you're good with macros and programming, much more can be done (like automagic part price updating).