Here are 2 tools enabling you to synchronize and automate the publication of your posts on social networks.
Here is an example. You just published a new article on your blog and you want to relay the information on Twitter, Facebook, Google+, and Linkedin.
With these tools all you have to do is to write your message, choose the social networks you want to post on, set the time (or let the tool optimize the time for you).
Et voilà: in 30 seconds you prepared a message that will be published on 4 social networks. Useful, no?