At work, I tend to have multiple instances of firefox open at once -- one for outlook web app, one for jira, another one or two for some in-house web apps... on top of this, I will often have a few terminals (tmux helps keep this to a minimum). I am very habituated to use alt-tab to switch between applications.
The problem that I have is that when I'm switching using alt-tab, all instances of firefox use the firefox icon, so I can't tell at a glance which firefox I'm switching to... yes, there's some text there, but I don't want to stop and read while I'm flipping through icons. Is there a way for alt-tab to display the favicon (the icon that shows to the left of the URL in a web browser) of the page rather than the firefox icon?
If you're using Ubuntu 11.10 or newer, you can press Alt+` (the key to the left of 1 and below Esc), to switch between the windows of the same application.
It shows smaller resolution images of whatever is shown in the windows. Below is a sample screenshot: