Here's a selection:
While iPhone users have Siri, Android supporters can talk to Alice. The app is based on a voice recognition system and is capable of learning. You can enter texts or operate applications by speaking. But Alice also answers questions or learns sayings. Those who would like to experiment with voice control can try it with Vlingo.
The Android Lost app allows for a lost smartphone to be located, disabled and if necessary have its content deleted from any internet computer. Similar functions are available for iPhones under http://www.icloud.com and for Windows devices at http://www.windowsphone.com.
This app provides product information at every turn. Point the mobile device camera at a barcode or QR-code in a store and Barcoo supplies a variety of information about the product.
There are also smartphone apps offering many of the functions of the well-known online saving and syncing service.
You are always trying to remember something, and if you don't write it down you may forget it. Enter Evernote. The notes, recordings, photos or files saved with the service are available through synchronising on every device with the Evernote app, which is available for all three major mobile operating systems.
Even on the go you may need to be able to view PDFs. The original viewer application for the format offers a good service to display and search documents. It is available for Android as well as the other major operating systems, Apple's iOS and Windows Phone.
Facebook, Twitter & Co
Of course, original apps from Facebook, Google+ and Twitter are best for mobile posting to social networks. For Twitter, there are other alternatives including TweetCaster for Android or Twitterrific for iOS.
Those who want to have maps of entire stretches of land or countries available to Android mobile devices offline can use Locus Free. This app allows for map information, predominantly Openstreetmap (OSM), to be stored in the smartphone's memory. An alternative is MapDroyd.
MX Video Player
This video player doesn't shy away from any format and can be controlled intuitively. It is however only available for Android phones.
It's mainly fun and games, but those who just cannot remember a song are thankful for this app, which after hearing only seconds of a song provides its name and artist, often with lyrics and videos.
Internet radio is unbelievably diverse and the TuneIn app makes the selection easier with thousands of catalogued stations and programs.
Why pay for text messages when you are online with your smartphone the whole time anyhow? The makers of WhatsApp asked themselves this question and came up with a comprehensive messenger solution. You can quickly send messages, photos and videos to friends for free as long as they have installed the app as well.