Brain Gym - Places to go for a good workout

1. Lumosity - Brain Games & Brain Training. Lumosity provides a good entry to the concept of a Brain Workout. It also allows for metrics implementation to track progress.
http://www.lumosity.com/

2. Myfitbrain - Brain Training, Brain Fitness, Brain Games, Brain Health. A collection of fun and interesting exercises. I need to spend more time on this one to be able to provide a more comprehensive assessment and perhaps my preference ranking.
http://www.myfitbrain.com/

3. Afunzone - Daily Games & Exclusive Puzzles. This site provides a huge (huge!!) collection of exercises conveniently categorized. Now be careful, it is a work-prevention site !!. It has two entry points.
http://www.afunzone.com/
http://www.afunzone.net/