Just a quick update on these links, here's a link for Google+
https://plus.google.com/share?url=[URL]
Now, if you want those links to open in a new window, just add this javascript code after the href's:
onclick="javascript:window.open(this.href,'', 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;"
This javascript code works with Twitter, Google+ and Facebook (maybe some other, but I haven't tested any other social networks).
Example for WordPress:
<a href="https://plus.google.com/share?url=<?php the_permalink(); ?>" onclick="javascript:window.open(this.href,'', 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,height=600,width=600');return false;">Here you can add text, image, whatever.</a>