Are there any good "brain training" applications online?

Here is my favorite:

http://chess.emrald.net/

It trains the brain to think faster , and you have your history and progress

I don't know of any prepared set of brain games, but if you want to make a real brain training games you should change the rules of the game every couple of days and have all kind of games - memory, strategy et cetera.

Otherwise the brain will know what to do next in the game instead of looking for a new way in a new game.

Here are some sites with brain training games:
http://www.entheosweb.com/flash_games/puzzle_game.asp
http://games.download3000.com/play/square
http://www.buzzle.com/games/MetroMatch.asp

Some comments to your answr:

1. The first link is not online , you can just DL the games.

2. The second link is online , but only for 4 times. I do not believe that it does anything good for your brain - did you try to play with those bubbles? After 4 times you have to register..

3. The third link is just a memory game. You do not have to force your mind on any subject.

Please try the chess link - it gradually fits your own level (if you just have a bsic knowledge) and it is sofisticated in its ability to @punish@ you by making harder challenges if you do it correctly and easier one if you fail.

I didn't proposed a prepared set of brain games, I wrote that if he wants to make a set on his own, he should have all kind of games - including a simple memory game that exercises your mind...

The purpose was not to play these spesific games, but to show types of games that exercise your brain in different ways.

According to your question it seems like you were looking for -
Lumosity

Lumosity is the brain fitness program designed by neuroscientists that is scientifically demonstrated to improve your memory, attention and processing speed.

Lumos Labs is the company that researched, developed and tested the Lumosity brain fitness program. Lumos Labs specializes in creating innovative applications of the latest developments in brain science in order to help people lead better lives. Since its formation in the spring of 2005, Lumos Labs has been consistently focused on researching and developing the most effective cognitive training applications.

There's a nice post about them on TechCrunch here.

Another two:

www.happyneuron.com

www.mybraintrainer.com

and much more info at www.sharpbrains.com/blog

If you are looking for solution for training and improving your brain,checkout