The most popular mobile apps of 2011

It's been a busy year for smartphones. And whether it's an iPhone, an Android device, a BlackBerry or Windows Phone 7, it's all about the apps. Apps for business and pleasure, useful and frivolous; apps that come at a price or cost nothing but the price of the bandwidth to download them – they've hit the market in their thousands. And some have done very, very well. 

Here's a look, in no particular order, at eight of the top apps of 2011. Most are cross-platform, though we’ve included one hugely popular iOS-only app.

Everybody has a Facebook app, it seems, and given the importance of the social network, it has to have a place in this list. With these apps, you can post updates, chat with friends, respond to notifications, and generally interact with your friends, colleagues and customers. More