Go find yourself a 16×16 icon and save it in the sociable-30 images\default\16 folder (assuming you are using the 16×16 icons).
Open the “services.php” file and add
'Google Plus' => array (
'favicon' => 'google_plus.png',
'url' => 'https://plusone.google.com/_/+1/confirm?hl=en&url=PERMALINK',
'description' => 'Google Plus',
),
— the entries are in alpha order, so I added it under the “Google Buzz” entry.
Easy as that.
