This will be a quick post.
I don't know about the rest of you, but every so often I just feel like my brain is getting slower. And I'm not even close to approaching the age when senility would be an acceptable explanation. Enter Lumosity.
The concept isn't new - it's just BrainAge, but it's on the Internet and it's free (for now). It's a collection of simple flash games that are supposed to gradually improve your memory, processing speed, etc. I'm a big fan of the attention game (mainly because I'm good at it) and addicted to the processing games.
I think what this and other IQ/ brain-improvement games do well is provide constant feedback on how you're doing. I think this makes the games incredibly addictive - you can essentially 'see' your brain 'improving' in 5 minute intervals. I think it's a stretch to say that these games really do improve your mental abilities; what's more likely is that you just get really good at figuring out how to work these games, with some tangential improvements all around. Either way, it's some good addictive fun.