EC2UI *Mod*
AWS has a wonderfulEC2 user interface that runs as a Firefox extension. It allows (among other things) for the easy control over instances.
Note: AWS has (improved and) rolled my code into the official release. The below mod is not needed any more!
The main way to "get to" a running instance is via SSH and instance DNS values are not known until run time. So it would be nice to have a method to launch an SSH program from the "Your Instances" pane to connect to the specified running machine.
Since this request has been repeated a lot on the tool's comments, I thought I would have a try at implementing it. I have made a supplemental extension that overlays the main one (version 1.3 build 15918) and adds this support. It is my first foray into XUL and XPCOM, so it may not be up to the stellar quality of my usual software 
With the overlay there are new preferences to control the ssh client command line. Click "Tools" at the bottom of the window:
The first item should be the full path to the executable. The next item is for the command line parameters. The DNS name of the instance will be appended as the last argument before launching the client.
To call SSH on an instance, just click in the context menu of the instance row:
What about the private key??
So how do we use EC2's magic public key loading so we can SSH as root to new instances? Well you could hard-code the private key file parameters into the command line... I like to use the PuTTY companion program called Pageant. It can keep keys loaded and find the right one for a given SSH session and magically apply it.
How to get the mod
- Download and install the main extension from AWS (link at top of page)
Then install my extension that overlays it.
The future
I have ideas for more features. Now that I know how to "extend" the primary extension I'll add more stuff over time. If you want to keep up to date, there is anAnnounce board that I update when a new version of something comes out.