Home Inventory app for the Mac and iOS

Keep important information about the items in your home in one place. Store make, model, serial numbers, purchase price and date, photos, receipts, warranty information (manufacturer’s, extended, and other types of warranties), and much more. Use the dated notes feature to make notes about modifications and repairs. Attach files, such as digital copies of owner’s manuals. No more digging through file folders and junk drawers to find the information you need.

Everyone really should be doing this, I think.