If idle hands are the devil's plaything, Satan must hate smartphones.
Androids, BlackBerrys and iPhones have so many good apps that their owners can fill the tiniest gap of free time with a productive, whimsical or useless activity.
Neuroscientists are debating whether this always-on approach is healthy for one's brain, but as that argument unfolds, you might as well have a little fun.
Here are my top picks for best time-wasting apps.
Games are a clear favorite for the stranded legions at subway stops and grocery store checkout lines, but this category has a staggering number of choices. Apple's iTunes Store helps narrow those choices with the Game Center, a selection of around 1,700 highly rated, high-selling apps, including 30 featured titles.
You'll find the usual suspects, like Angry Birds, Flight Control and Doodle Jump, which are perfect for situations when you have three free minutes. If you already have these games, try Let's Golf 2 ($5 on iPhone), Blokus ($5 on iPhone) and Tetris ($1), or newer games like Trucks and Skulls ($1), Astronut (free) and Zoo Rescue ($1).
Android users have fewer choices here and elsewhere, because many game developers have only just begun working on this platform. Among other things, developers were losing money on Android users who, until recently, could "test" a game for nearly 23 hours and 59 minutes and then request a refund.
That said, Android has Angry Birds, Let's Golf 2 and Tetris, which are all solid choices. Glu Mobile, the maker of many popular and free iPhone games, like Gun Bros and Deer Hunter, will introduce some of those games to Android in the coming weeks. Gun Bros is expected to appear this week.
BlackBerry users who are accustomed to second-rate apps have it slightly better when it comes to games. The genre's most famous mobile games are missing, but thanks chiefly to Electronic Arts, great ones still await, like Need for Speed Shift 3D, Yahtzee, Tetris and Risk. All sold for $1 apiece for iPhone devices last week.
Heavy I.M. users who can't bear to be away from their instant messaging accounts can continue their conversations on the smartphone with BeejiveIM ($10 on iPhone and BlackBerry devices, $5 on Android). The app offers a seamless experience with all the major desktop or Web-based I.M. systems.
Few things kill time more effectively than Twitter and Facebook, of course. The Twitter app, from the company, is now better than all the other apps that purport to help you follow your feed. It's free on the iPhone and Android phones. Research In Motion has built a good free version for BlackBerry.
Facebook's official iPhone and Android apps are also free and highly rated. No official Facebook app yet exists for BlackBerry, however, and the R.I.M. version has earned poor reviews.
For those who believe that Twitter, Facebook and smartphone games will rot your brain -- or who simply can't get past Level 1 of Angry Birds -- I.Q. boosters are a good option for killing a few minutes.
Brain Fitness Pro ($4 on iPhone) can be tough -- like boot camp for the brain, as one iTunes reviewer characterized it. Through a variety of timed quizzes, it promises to improve your short-term memory and problem-solving ability. Brain Tuner ($3) is featured in Apple's Game Center; skeptics can try Brain Tuner Lite, which is free.
Brain Genius Deluxe (free on iPhone and Android), from Glu Mobile, is highly rated. Same goes for the BlackBerry app, Brain Up.
For a different sort of brain-building activity, crosswords do nicely. Try the Crosswords app ($10 on iPhone and iPad), or the NYTimes Crosswords (free for first week, then $2 a month or $17 a year). On Android, go with Shortyz Crosswords (free).
Many people have abandoned crosswords for Sudoku. For them, the Sudoku app ($1 on iPhone) from Electronic Arts offers thousands of grids and five difficulty levels. Android users have an even better alternative in Platinum Sudoku ($3) from Gameloft. It includes 640,000 grids, five difficulty levels and automatic error checking.
Because we're talking about processing bite-size pieces of information, poetry deserves a mention. And while a grocery store checkout line may not seem an obvious place to consume poetry, the Poetry app (free on iPhone), from the Poetry Foundation, makes it easy to quickly discover new poems and writers. You can mark your favorite works for future exploration, too.
Sometimes I like to be productive in those odd minutes, rather than waste time. In those instances, I'll sometimes open my SoundHound and Shazam apps -- but not to identify music. Rather, I'll buy some of the songs I've identified with the apps in recent weeks, and which these apps keep in neat lists.
If I have the children along for errands, however, I can forget both productivity and mobile gaming. Few sights are as sad as a child watching a parent who is lost in a video game.
Storykit is a free iPhone app parents can use to quickly build picture books with children, using on-the-spot photos or old-school tales that are ripe for rewriting.
For parents of middle-school children, BrainPOP is a worthy app, featuring a new brief educational cartoon every day. The cartoon is followed by a quick quiz that will at times challenge even a grown-up.
Finally, one of the best things you can do as you wait in line is go to the App Store and peruse all the updates to the apps you already own. Some of the updates are important, others merely incremental. (Hint: if the version number is 1.5 or 2.0, it's more important than 1.2.7.5.)
With big updates, it's almost as if someone has given you a new app. Take a few minutes, download the important ones and take them for a test spin. Angry Birds can wait until your next set of errands.