I'm on the Mac so I use Numbers. I've never been any good at figuring out spreadsheet programs so if anyone knows how to get cool looking graphs out of the data I'm all ears.

The categorise I use are
Code:
Year/Company/Line, Class, ID Number, Toy Name, Characters per package, Sets in collection, Retail price, Total retail price, Package condition, Figure condition, Current Price, Notes.
I update the current price once a year and use the best realistic price from eBay , RK or BBTS.