Generally my IDE (VS2008, Notepad++) does it for me while I write. Whenever I edit code, I usually need to do it myself. Though whenever I'm doing something quick, especially for responses on this site, I'll use VIM or gedit and I do it manually.
I certainly don't use anything to auto-format my code after the fact (though these tools do exist) unless I am conforming someone else's code to our coding standards.