Digital Camera User Manuals
This site can even be better than the manual that comes with a camera, as it includes simulations and interactive demonstrations of using various camera models.
You will have to pay for a manual here (reprints). If you are having a tough time finding your manual online, or you really like having a hard copy and hate printing so many pages, this is the spot to go. This site has almost every manual in existence.
This site includes an exhaustive list of manuals available for download, or you can buy the paper versions at the site's eBay store. It includes newer models, of course, but also has many older cameras.