Google plus the new social network of Google do not have directly option that you can share your updates with your Facebook and Twitter friends. But adding a simple Google Chrome extension will give you the option that you will able to share your updates in Facebook as well as Twitter.This extension will add a simple send to to each of your posts. Once you have click it, it will bring up a new internal dialog box asking you where you would like to share your post.
To add this Google plus extension in your Google Chrome browser click here
I guess there is only two option in the extension Facebook and Twitter share but i hope soon we will have more social share options.