What if a simple mental exercise could improve your memory and intelligence?
A study published in PNAS, an important scientific journal, shows that a particular memory task called Dual N-Back may actually improve working memory (short term memory) and fluid intelligence. This finding is important because fluid intelligence was previously thought to be unchangeable. The game involves remembering a sequence of spoken letters and a sequence of positions of a square at the same time. Fluid intelligence is the ability to find meaning in confusion and solve new problems. It is the ability to draw inferences and understand the relationships of various concepts, independent of acquired knowledge.

Brain Workshop is a free open-source version of the Dual N-Back mental exercise.

Here is a flash version of Dual N-Back mental exercise:

More Info:
Brain Workshop Website
Wired article for an introduction to the Dual N-Back exercise and its benefits
Read the original research paper by Jaeggi, et al. (2008)