I wanted to say that you use calculated columnns, but unfortunately according to this link the TODAY function is supported as a default value, but not supported in a calculated column.
So, outside of a default value, the only way to do this may be through a more involved effort. I see two options:
Use SharePoint Designer and the Data Form Web Part to show a view into a list with an additional column that has today's date.
The right way to do this is likely a computed field as it does not involve storing any additional information, but simply displays additional information. I didn't find a good link that only discussed computed fields, but this link does go into a bit of depth.