iPhoto2Gmail is a plugin for iPhoto (software to manage photos by default in Mac OS X) that integrates the Gmail service. This tool works only on Mac OS X, Windows users can use Picasa which is an application that offers the same functionality .
With this plugin we can send our photos from iPhoto using our Gmail account, besides having the option of using our contacts in Gmail, so the process is simple and fast.
At the time of sending the images this tool gives us the ability to resize images, f your pic is already smaller than 800×600, you just send it “full size.” If it’s larger than 800×600, then select the “Send Scaled” option and it will shrink it to 800×600, which is generally small enough for you to send to most people. iPhoto2Gmail works with iPhoto 5 and iPhoto 6 and it’s Universal Binary.-
I think as Mac OS X lacked Picasa, have developed this plugin to integrate with Gmail for managing photographs of Mac.