Is there a single PHP API to post to multiple sharing sites (Twitter, Reddit, Linkedin, etc)?
Good question, I know a lot of people use hootsuite to update multiple networks however I didnt see anything about an API on their site. In searching i found two that looked ok and offered APIs. They both update ~40 services however I didn't see reddit or youtube. You can check them out though, maybe you're able to link one account to another like facebook lets you do with twitter. Anyway the sites are:
http://ping.fm
http://hellotxt.com