Facebook, the popular social-networking site, has unveiled new ways for its members to use their Facebook profile on other websites.

The service, called Facebook Connect, will enable a user's social-networking profile and log-in details to act as a web "passport", giving them quick and easy access to other sites that might be of interest.

These include Digg, the social-bookmarking site that allows people to discover and share things they find online. For example, if you wanted to add an interesting article or website to Digg, a login box will either prompt you to enter your Digg user details if you are already a member, or your Facebook username and password.

If a user opts to use their Facebook details, then information about the article or website they have added to Digg will also appear in their Facebook profile, and they will be given the opportunity to connect on Digg with people who appear in their list of Facebook friends.

"Facebook believes that enabling users to take their identity and network of friends with them around the web, while trusting that their privacy is protected, makes the web as a whole more open and connected," said Facebook in a statement.

So far, 24 websites have signed up to be part of Facebook Connect, including Digg, the blogging website SixApart, microblogging service Twitter, and the online city guide Citysearch. The site's founder, Mark Zuckerberg, hopes that number will increase as developers begin to see how the service provides seamless connections all around the net.

"Across the web, content creation has become easier and more immediate, resulting in a continuous stream of information through what we call feeds'," said Zuckerberg. "The power of feeds on Facebook is their ability to move you into a world where you receive relevant information in a social context, wherever you are on the web."

Many web developers hope the new Facebook "passport" will encourage more people to use their sites, as they won't have to register for them individually, but can instead use a single sign-on. It will also act as a form of word-of-mouth advertising for these other websites, because details of the site will appear in Facebook users' profiles, and effectively act as a personal recommendation to everyone in their friend network.

Facebook is currently in the process of overhauling the look and feel of its website in an effort to improve members' user experience. Some Facebook users had complained that the site felt cluttered and untidy, but the new layout, which divides areas of a member's profile into separate "tabs" is designed to streamline the user interface. The new-look site will be rolled out to Facebook's 90 million active users over the next few weeks.

Facebook also pledged to continue with its process of internationalising the site. More than two-thirds of all Facebook visitors are based outside the US, said Zuckerberg.

Facebook Connect, which was first announced in May this year, will not be rolled out across the social-networking site until the autumn. It faces competition from a similar service backed by rival social-networking site MySpace, which recently launched its own Data Availability project, as well as from Bebo, which has signed up to Google's OpenSocial project that allows third-party applications to work across multiple websites.