Right now I use a Palm Tungsten C for general use. On the Palm TC, aside from the included software, I use "SmartList To Go" and "Thought Manager". "Thought Manager" is much quicker for re-organizing information than a spreadsheet. It is primarily an "outliner" programme.

Example:

Tamiya TA05:
__Orion 19T motor
____[a bunch of notes about the Orion motor ... ]
__Futaba S9550 servo
____[a bunch of notes about the Futaba S9550 servo ... ]

If I have the above in an outline, then I can "clip" the Futaba S9550 material and move it to another car (like a word processor), or hide the data and just see the name.

It is also possible to attach drawing to items in "Thought Manager", which is very difficult to do in most spreadsheets and even some databases.

"SmartList To Go" is a full relational database which a fairly easy to use front end. I have barely started using it for RC because I have only recently gotten involved in RC again, but I have been using the software for a few years for a number of other things (such as tracking the cost of groceries). I expect I will eventually be using it a lot for RC too.