Stockfish, Firebird & Houdini are all free & very strong...assuming your PC is up to snuff for them. But since you need a program (some or all of these engines are just that, with no GUI) Fritz 12 is very popular and pretty strong, Rybka is another good program. If you have a heavy duty PC Fritz has a super-strong program available (it's more expensive & I doubt if anyone who isn't a professional really needs it, unless money is no object for you)
Fritz 12 also comes with a multi-million game DB which you can update via The Week in Chess free downloads of current tnmt/match games. So if you can afford it I'd say buy it or Rybka, you could also look around for Fritz 11 or 10 cheap at amazon or eBay.
As for Fritz 12's analysis I've found it disappointing many times - it shows me the point at which I was OK and then skips several moves to announce that I was now busted...without any suggestions on how to avoid getting busted. On the other hand it has also shown me lots of stuff both me & my opponent missed in some of my other games. Here's a link to tons of info on Fritz 12:
http://www.chessbase.com/shop/product.asp?pid=467
Hey guys,
I'm an improving adult player, and I wanted to start a discussion about what engines, databases, and such you guys are using. I have the freeware chessbase light, and am considering upgrading to the chess base light premium. I have seen a couple free alternatives but I really like the positon search and opening report functions of chessbase, along with the eBooks available for their format. What are your thoughts and experiences? I mostly use this program to study openings and master games, not for computer analysis. So far I have been using the computer analysis on chess.com quite a bit, but I sometimes wonder about the moves the computer likes. For example would fritz or rybka give me more useful analysis? I am sure some people will respond, this isn't important at your level, study tactics puzzles, and the like, but I already do that, and this isn't a thread about general improvement. I just want to take about good chess software, and their pros and cons.