Facebook, Twitter, Google - Create large share buttons using JavaScript

This post is not like my other posts (ADF & Java), It is about creating custom large share buttons for Facebook, Twitter and Google+
Actually this share functionality of social networking sites (Facebook, Twitter, Google+ etc) works on a particular url pattern

Let's take example of Facebook , to share any url on Facebook just pass that url as a parameter in this url
http://www.facebook.com/share.php?u=url
See when i open this url on browser (I have passed www.awasthiashish.com in url parameter)
http://www.facebook.com/share.php?u=www.awasthiashish.com , it shows standard Facebook share page