I use VirtualBox to run Linux instances for development on my Mac and Windows desktops. Since I don’t use a GUI with Linux, just SSH, it’s convenient to run the virtual machines headless i.e. without displays. This is something the standard VirtualBox GUI doesn’t allow. However, there are two great utilities for Mac and Windows that support this.
VirtualBox Menulet for the Mac shows a dropdown list of all your VMs and their status. Select one to launch or shutdown. Slick and effective.
VBoxHeadlessTray provides similar functionality for Windows. It prompts to your to choose a VM and then launches it in headless mode. A icon in the system tray allows you to start and stop the machine and launch a remote desktop connection to it.
Now to find something similar for Amazon EC2.