http://twitter.com/share?text=<TITLE>&url=<URL>
E.g. http://twitter.com/share?text=This+is+google+a+search+engine&url=https%3A%2F%2Fwww.google.com
http://www.facebook.com/sharer.php?u=<URL>&p[title]=<TITLE>
E.g. http://www.facebook.com/sharer.php?u=https%3A%2F%2Fwww.google.com%[title]=This+Is%2C+Google+a+search+engine
http://pinterest.com/pin/create/button/?url=<URL>&description=<TITLE>
E.g http://pinterest.com/pin/create/button/?url=https%3A%2F%2Fwww.google.com&description=This+is+google+a+search+engine
Thought I would add the url for Linkedin. I just deployed this on my blog and works beautifully.
Linkedin
http://www.linkedin.com/shareArticle?mini=true&url=[path]&title=[title]&summary=[description]&source=[domain]
More info here: https://developer.linkedin.com/documents/share-linkedin