What brain games do you like?

I like the Dual N-Back "Game". It's the only brain game that has any scientific validity.
Shameless plug: I wrote a version for the iPhone called IQ boost.

(iTunes link ) http://itunes.com/apps/iqboost

It very closely follows the protocol from the study that showed it's effectiveness.
http://www.pnas.org/content/early/2008/04/25/0801268105.abstract

There are also a number of free implementations on the web.

http://dual-n-back.com/
http://www.soakyourhead.com/

I've always like indigopuzzles.com It's got Hashi, Sudoku, Kakuro, and Hitori. Nice size archive of each, and can eat up a fair amount of time.

Actually, I think the book may still be open on brain games and how much they help cognitive aging. I don't study it, but I think people are starting to find that physical exercise may be much more effective than 'mental exercise.'
Still, thinking is fun. But one of the things I've noticed about brain games is that they're often non-social in nature, yet, social cognition seems like it could use practice too. So why not play a cooperative board game, like this http://en.wikipedia.org/wiki/Shadows_Over_Camelot

Check out Numbrosia. This puzzle is original, difficult, and can be highly addictive.

The game set (at http://www.setgame.com/) is an excellent visual pattern-matching game.

Nothing beats Zoombinis! My kids grew up with them, all the disks, and I to this day sometimes play.

Oh man, I definitely love the Washington Post's crosswords! Have been doing them since high school. I'm pretty sure they offer two puzzles every day nowadays-- you could spend all day working on those things!

And to Coturnix, Zoombinis and I go waaaaay back. I still have dreams of a tree-creature shouting at me, "MMMMAKE ME A PIZZA!"

Thanks! Your post caused me to look up "Jumble" (one of my favorite word games) on the Web, and sure enough they have a site that looks worth exploring:

http://www.jumble.com/

Also, growing up, I loved a 2-person game called "Jotto" that has some online versions (but I don't think it's sold in stores anymore?)
For some reason, despite loving math, the recent slew of number-related games have never much appealed to me, but thanks for all the recommendations to check out.

I particularly like pic-o-cross.

This is my current favorite site.
http://www.conceptispuzzles.com/

Has a huge variety of number (like sudoku/kakuro) & picture puzzles (like pic-o-cross, link-a-pix), updated weekly. It has samples in the landing page, but to get the weekly puzzles you need to create a log in, which will also save your work that can be accessed from any computer.

Anyone remember Wff N Proof? Learned logic from it at age 8. Served me well ever since. Crosswords and sudoku are standards around here. I try to do the easy sudoku fast and clean (no notes). Crosswords are always in ink - a thing I got from my dad who could finish the Sunday NYT puzzle in ink. I miss him.

Lots of interesting suggestions. Shecky, great link to the Jumble site. I've been looking for something like that.

Tangrams reminds me of Tantrix, another tiling game: http://www.tantrix.com/ . Lots of ways to play, and apparently can go deep as heavyweight games like chess. I've only played against a robot online but it's worked smoothly.

I recently caught Daniel Amen on PBS. He likes table tennis for the brain and compared volleys to chess problems, mixing sport with game play without all the physical hazards.

Somewhat along those lines, they say that juggling measurably increases grey matter. I suspect it's not just a hand-to-eye thing either. Working out patterns is not dissimilar to solving puzzles. That stood out in stark relief for me as I learned to do a 5 ball cascade, which took a long time BTW. You have to get a handle on the rapidly moving pattern before you can fully address the coordination issues. (It's not a simple extrapolation from 3 balls.)

Learning to swap hand positions during a 3 ball cascade nearly caused me to short circuit -- sort of like those sci-fi robots that melt down when confronted with a logical paradox. It was weird, I can tell you that much.

And there's an expressive aspect to it as well. There's even literature out there on the mathematics of juggling for those more savvy than I am.

How do you define "brain game"? Does it have to be a game of perfect information, or can it be one that involves probabalistic reasoning? Does it have to be difficult, or is it enough that you have to think at least a bit in order to win?

The solitaire card game that I invented and have implemented online (Elemental) is pretty easy - I'd say that a beginner can expect to win 50% of the time and an expert player playing optimally up to 80%. If that's too easy you can always increase the challenge, e.g. by aiming to win ten games in a row or something. It's not always solvable and the best probabalistic reasoning doesn't always pay off. But it helps.

Of the online games so far suggested in the comments, Numbrosia, suggested by Amir Michail in #4, is the one that most tempts me to devote some time to.

I found out about a lot of different kinds of puzzles that can be played online (like Kakuro) through the old US/Google tests for the World Puzzle Championships (http://wpc.puzzles.com/ see History to download them). All these puzzles are language-neutral.

My favorite is the logic puzzle Fences, also called Slitherlink, Number Line, or any number of other names. One place to play it online is at http://www.kwontomloop.com/puzzle.php . See also http://en.wikipedia.org/wiki/Slitherlink .

I'm fond of killer sudoku, which is a nice combination of kakuro and sudoku. There is at least one site providing daily puzzles, with a nice interface for playing online (or just allowing you to print a PDF).

I like Shikaku. There are other logic games linked at the bottom, but Shikaku is my current fav.

Oh, and for those who prefer word games, there's Babble (sort of a cross between boggle and scrabble).

I read lots of claims about the so-called "evidence" on games impact on the brain. Yet, I see no evidence from any formal studies. Yes, it makes sense, but how much game playing is needed, how often, which games. Let's stop the games-claims and show the evidence.

Chess. http://freechess.org/
See also: http://en.wikipedia.org/wiki/Chess

I like playing Jewel Quest on my phone. Simple puzzle games keep me occupied for hours on end.

I also enjoy Guild Wars (http://www.guildwars.com) trying to figure out what spell/weapon combos work the best (splinter/barrage ftw!)

I play The Sims 2 (http://thesims2.ea.com) because I get to sit for hours designing houses and arranging the furniture. It's a really creative outlet for me. I also love making new characters, designing their facial features, and then breeding them like a mouse colony to see what kind of kids I get. I use cheats to speed up the process. It's so much fun!

And Jim: I say, let's stop the game-claims and just play the games! ^_^

I know of a truly engaging and quite elegant (which is rare) free online game called Auditorium. Visit it at

http://www.playauditorium.com/

You have to turn your speakers or headset on to enjoy the game. It's like listening to... well, you gotta experience it yourself. I was rather blown away.

Chess:

www.playchess.com

The brain games on this site are really unique & fun:
www.braincurls.com