Add API features (LinkedIn, Google+, etc..) to existing website

The website allows users to register. Once the register they can link to their facebook and twitter account through respective API. When they do this a post is made on their wall on facebook and twitter (e.g "Just registered at [login to view URL]). They also get a direct link on their userpage on our website. You can test this by going to [login to view URL] and click search. Search IN735047755 and you will get an example profile where the F and T icon are linked to this users facebook/twitter. Now I would like to add LinkedIn, Google+, Picasa, Youtube, etc.. API's. For LinkedIn and Google+ I would like to have a post made on the wall when they link to respective media. Please see attached document for all details regarding project requirements.