I found the Super Invite Comment Script really useful, so I've extended it with some extra groups.

If you would prefer to use the original, it's here

This script gives you drop down boxes to comment and invite images to groups. (See below)

To use this script, you will need to be using FireFox browser. You can download that here

Next, download the google toolbar here

Now you need to download the greasemonkey script for firefox here

Lastly, you're ready to download the greasemonkey script for Flickr Super Invite Comments (SIC) I think it will install itself if you click on the link. SIC Download