Is it OK to use info such as city population, or ZIP codes, etc? "Absolute" type info so to speak, facts. Let's say I post such info, can someone claim CopyRight infringement? I mean I would probably have to borrow it from a website, not necessarily governmental.
The "facts" cannot be copyrighted. The way you describe the "facts" can be. If you go to a site and copy the creative phrase "Bluesville has 24 shiny happy people living within the town limits" you can get sued, but if you change it to "Bluesville has a population of 24" that's ok.
It IS ok to copy the phrase "Bluesville has a population of 24" because there is nothing creative about that phrase.
Save yourself some headache, go to Wikipedia where they give you a license to steal their info. Just be careful of the duplicate filter.
Use stuff from the Census Bureau or other government sites. If you are American, you are already paying for the information. If you are not, well, you probably can still use it. The CIA factbook is a great resource too.
However, everybody and their mother uses this stuff. You will need to change the wording to avoid duplicate penalties.