Free chess engines

If you want a chess engine to analyse your games there are many to choose from. If you want a commercial engine there is Chessmaster which is good beginners and intermediated players. I think perhaps even more advanced players could still get something from it. However they usually move on to Fritz or Rybka. I admit to having all three. They all run natively on Windows however. What if you want to use another operating system say Linux? Well there are lots of free chess engines available on the internet. The one I suggest is stockfish since its available for all the major operating systems. http://www.stockfishchess.com/
There are lots of other chess engines available to choose from at http://www.superchessengine.com/ and if you want to use Winboard as your interface to the engine its at http://www.tim-mann.org/engines.html I found a very interesting piece on a free chess engine called Firebird which may be a clone of Rybka it may not be but personally I won't be using it. If it can be proven that it isn't then I'll certainly give it a try. http://www.chessvibes.com/reports/chess-engine-controversy/ If you don't want to use winboard with the engine of your choice you can use Arena. http://www.playwitharena.com/ I have used it but I don't like its analysis feature. I'm probably a little spoilt but I prefer Fritz or Rybka with Aquarium for computer analysis. Give arena a go anyway and let me know what you think about it.