Custom application development has exploded since iPhones were released and social networking sites took off. Of course custom applications have always been available but many companies are taking advantage of the way these new technologies have been created, to develop special applications for everything from keeping track of your exercise program to finding bookstores in the city. Social networking sites like Facebook also allow you to create and publish custom applications and have people show these on their profile like a badge of honour.

Another sub-category of customised applications are those called "Widgets". These small applications usually perform a single function and don't cost too much to develop (in comparison to a mobile application). For example in Facebook, you can download a widget that shows parts of your Facebook profile and you can publish that widget to your website (see examples in the Facebook Widgets) to encourage your website visitors to connect with you.

Before you think that you aren't a software developer and can't develop a custom application, you can always employ a developer to do it for you. The opportunity to create an application and have it sold or given away as part of your marketing campaign is huge.

Let's take the fictitious example of Mary's company, ACME Personal Styling:

Mary decides she wants to create a fun application on Facebook where people can choose their virtual clothes for the day and have all their friends see what they are wearing. In the application, you could go for a gothic look or traditional Japanese outfit or whatever you like to match your mood or an activity you are doing that day. Mary's application takes off and thousands of people around the world have their personal fashion plastered on their Facebook pages. In the bottom right hand corner of the application is Mary's business logo with a link to her website. Mary is getting thousands of people see her application, click on the link to get their own copy of it and attracting new visitors to her website from all over the world, dramatically increasing her potential customer base. Some will buy and others will just use the application – either way the exposure becomes massive and a newspaper picks up Mary's application and she subsequently gets interviewed in the newspaper, TV and magazines.

This is an example of where custom applications can go "viral", with the ability to create massive exposure for a company. Many times you won't get this effect but it is possible to make a decent income from an application or simply increase customer satisfaction by providing it to customers and website visitors as a gift.