Pinterest has unveiled new mobile apps for its social networking pinboard service, with the introduction of Android and iPad applications while refreshing its iPhone app.

The move comes shortly after Pinterest shed its invitation-only policy and opened its registration to anyone.

Both efforts should help Pinterest increase its user base, which already shows strong user base numbers.

Earlier this week, online traffic tracker Experian Hitwise reported that last month, Pinterest was the third most popular social network. The pinboard site garnered 119 million visits, compared to 250 million at Twitter and 7.5 billion at Facebook.

"It may sound funny, but our goal has never been to keep you online," the company said. "Instead, we want to inspire you to go offline and do things that you love. Today, we're making it easier to take your inspirations with you by providing new apps for Android, iPad and iPhone."

The new apps are available for download at Apps.Pinterest.com.

Cashing in on the burgeoning mobile market is important to any social network.

Facebook, for example, has taken hits from industry and financial analysts for not yet having a way to monetise their quickly growing mobile user base. In documentation filed with the US Securities an Exchange Commission prior to Facebook's initial public offering earlier this year, Facebook's lack of a mobile plan was categorised as a "risk factor" for investors.

However, this isn't a problem for Facebook alone. It's the same for all social networks.

With mobile apps, Pinterest is taking the first steps not only to reach out to potential mobile users, but also to eventually generate revenue.

The company noted that its Android app is custom-designed for both phones and tablets.

For iPhone owners, the redesigned app features a two-column layout that lets users see more pins.

iPad owners may have been given the best Pinterest experience with the new and redesigned apps, the company said.

"The iPad app offers users new ways to engage with pins, whether swiping the screen to resume browsing after viewing a board, or using the embedded browser to see what others are pinning from their favourite sites," the company said.

Pinterest is like an online, shareable scrapbook. The site is a collection of collections, which offers a look into the worlds of food, athletics, fashion and travel. The site is set up so users can create pages of interest by pulling in images from around the web. If a user spots an image - of, for example, an interesting hairstyle, piece of pottery or culinary dish - she can use a plug-in to grab it and "pin" it to her virtual board.

People who follow the user can see her pinboards, repin their favorite images and comment on them.