Your lawyer, your insurance company, your executor, and your family may love you for this Home Inventory Guide one day, though only one of the latter is likely to help you complete this guide:
Via Neat New Tricks (which also links to this Picanswers site – gotta love the web), comes this: Home Inventory Guide
It’s a California guide so don’t phone them for help, unless you live in California! Phone your own state’s “people.” (You DO have People, don’t you? If you don’t know who they are, phone your public library reference staff – they are Your People.)