Top sources for opening theory Can anyone recommend any good sources such as periodicals, websites, or what not to stay up to date on the latest opening theory? I am willing to pay if the source requires such. How do the top Grandmasters stay up to date on the latest theory?
The top players in the world keep up with theory by actually looking at the latest games to be played. Every week, Mark Crowther collects all available games and prepares them in downloadable format here: http://www.theweekinchess.com/.

For players who can't look at a new move and instantly tell the ideas behind it (pretty much everyone below FIDE 2600), there is the Chess Informant: http://www.chessinformant.rs/. It comes out 4 times a year and has been in publication since 1966. It won't keep you nearly as current as checking the TWIC games every week but it will at least have someone to explain the moves to you.