Much of the talk around Groupon recently has centered on its impending IPO. Regardless of whether you think it’s a good or bad buy, or a good or bad idea; the reality is that daily deal emails have entered into millions of everyday lives.

One of the biggest reasons that Facebook has become such a behemoth was the introduction of a simple feature. The ability to tag your friends in photos and have those tags show up in friend’s news feeds was revelatory. Ask any early Facebook engineer and they will tell you that people literally spent hours just clicking through hundreds or thousands of photos of their friends. Photo sharing is still a hugely popular field – with tons of people competing for your snaps. These guys are making a lot of the headlines at the moment.

Behavioural economics is something that numerous online and mobile platforms have tried to corner in the recent past. Rewarding people for their behaviour and engaging with them in order to encourage loyalty is something that Foursquare, SCVNGR and many other startups are already doing. Kiip are one of the most hotly tipped companies in this sector at the moment.

There’s has been a huge amount of hype around mobile apps since the New York Times declared a Gold Rush two years ago. Clients are being quoted absurdly high prices for apps. Businesses are developing them purely on the basis that ‘we need an app’ without thinking of how to promote them.

The reality is that they are important. They’re not expensive. They do require a little thought though. Here are two of the best companies active in this sector at the moment.

In an era where you’re competing with umpteen websites, Facebook feeds, Twitter streams and mobile apps – promoting new books and publications can be somewhat daunting.

Over the course of the next few days, I’ll show you a few tools that are highly effective, low cost (or free) ways of promoting books and authors, engaging with readers and generally doing all you can to sell more books.

The first area we’ll look at is audio. Often overlooked in the rush to create YouTube videos or trailers; audio is still hugely popular. I can honestly say that there hasn’t been a project that I’ve worked on where the number of audio streams accessed or number of podcasts downloaded hasn’t ended up surprising me and my clients alike. It’s definitely worth thinking using a tool like Soundcloud as part of your promotional efforts.