A few moments with google, using search items like "brain exercises" will immediately bring you to a large number of web sites that offer to improve your mental function, combat the decay of mental performance with aging, etc. Some of these have appeared since my previous posting which listed several. A recent NYTimes article (from which the graphic on the left is taken) points to a number of these sites and offers an interesting discussion.
I have held back from taking the plunge into brain exercises, partly because I'm afraid of what I might find find out about how far gone I already am, and partly because some which appear to be most thoroughly researched and academically respectable want your money. But, now happy-neuron.com has offered me a free login to try out their regime, and so I have taken the bait. I will be offering my opinion of this site after immersing in their 20 min exercise sessions for a few weeks, and if I have the stamina or remaining self-esteem (and get offered a free login), will review some of the other sites in subsequent posts.