iPhoto2Gmail

Link: Apple - Downloads - Email & Chat - iPhoto2Gmail.

This is one of the things that can be done with MailPlane yet here is a free plug-in that allows you to easily send iPhoto pics via Gmail.

About iPhoto2Gmail
An iPhoto 5 , 6, & 7 (‘08) plug-in that lets you quickly and easily send pictures using your Gmail account… all without installing or configuring an email application.

You can choose to have the pictures resized and sent as JPEGs for quicker emailing, or send the full sized original files. iPhoto2Gmail features Gmail Contact list integration, so emailing pictures to your contacts is even simpler.