Ping.fm is most effective way to promote your blog post on different social networking sites without loging in those sites,see the below image to list of supported social networks.
Finally but not lost see the complete list of supported social network sites,you find some other popular social sites haven't been logged in, And create account in those sites and access it.
Note::Don't access your blogger account because when u ping any thing in Ping.fm, that make's as a post in your accessed blogs.