Simple LinkedIn PHP is a library for interacting with the LinkedIn API. The library was designed and tested for PHP 5.2+ and is not expected to work with PHP 4. The only prerequisite for Simple LinkedIn PHP is the PHP cURL library.
There have been a lot of new socially based mashups showing up recently. In fact, we recently topped 700 social mashups. While many of these use the Facebook API or Twitter API, there are many more social APIs. The mashups below run the gamut, though, yes, also include Facebook.