These are some of the memory apps I have tried so far:
1. Lumosity: The presentation and quality of the games are fine and varied. I'm a bit skeptical of the science involved since the goal for most people is to prevent dementia and maintain function, not just improve function. Unless you have a stroke or some other cataclysmic event, dementia generally develops quite gradually. It is this silent, slow progression which makes it so creepy and frightening.
Putting that aside my other complaints are that I found the puzzles either so challenging as to be frustrating or too easy. It may just be me, but emotionally I found the experience to evoke feelings either of smugness or incompetence. To me that is not helpful. Also I didn't like their model (which may have changed since I played) of so many free sessions and then no access. Naturally one of their goals is to make money, so I can't say I blame them, but to expect someone to really see results and appreciate their product over 2 weeks is unrealistic.
2. Clockwork Brain: I really enjoyed the puzzles in this game, and the artwork, Steam punk themed, is gorgeous. I got it when it was newish, and was frustrated by the lack of new challenges. Since that time they have expanded.
3. My current favorite is Elevate. It focuses on verbal skills. It has definitely helped me tackle some of my chronic spelling weaknesses. It automatically makes challenges more difficult or more simple depending on how you are doing right at that moment. You play each game until you finish the mission, whether it's making a small flock of birds fly, reaching a distant planet in the Space Shuttle, building a shape, etc. This makes the emotional feeling one of success and of overcoming a realistic challenge, even if the score for the day is worse. As you play your score ranking (across all users) gradually goes up, if you play regularly. It keeps track of your playing streak. It does not take a lot of time to get through the 3 games a day you can play for free, and there is a lot of variety in terms of the games, some are auditory challenges, some more visual, some use a combination of visual and auditory techniques to improve memory. I have no idea if it "really works" in a scientific sense. I remain skeptical since I believe we are still in the baby stage of learning about learning. I do know that I look forward to my several minutes of "training" each day.
As I find new apps I will update this post and "bump" it.
And if anyone has similar apps they enjoy, please post a comment. I review the comments before they appear so you won't see it right away.