It is kind of complicated actually.  There is some stuff that is straight forward.  Published before 1923 is public domain. Anything else has other criteria.  Here is a guide.  That is all for the US, so it may be different elsewhere.
Here are a couple sources of Public Domain documents in ready to use electronic format:
Project [...]

I am throwing my first large scale LAN party.  Since this Saturday, March 17th is St. Patrick’s Day I am calling it Luck O’ the Irish LAN.  We actually had reserved the room for another purpose, but that didn’t work out, so a last minute change of agenda led to this LAN.  I expect it [...]

Windows Vista Hinders Creative Users’ Efficiency Even More than Windows XP Did
From Slashdot. Rather interesting. Basically they say that the mouse precision and menu lag are worse in Vista then they were in XP, which has a negative impact on productivity. From my usage of Vista I can concur. I even [...]