Multiple sites have buttons where one can tweet, digg, etc. On this site you'll help you can buttons for six sites (search twitter and you will discover their whereabouts).

It is possible to lib or api i'm able to use to create these buttons?

Have a quick consider the web addresses the buttons connect to.

This is actually the one for twitter:

http://twitter.com/home?status=Check+out+http%3A%2F%2Ffav.me%2Fd2nh4ae+on+%23deviantart

As we undo the url-encoding this is exactly what we'll get:

http://twitter.com/home?status=Take a look at http://fav.me/d2nh4ae on #deviantart

You do not need a library to create individuals, it is simply quite simple string manipulations. All that you should know may be the format for that specific discussing site (which you'll snatch no matter where) and also the url for that page you need to share.