A system plug-in called Choosy is trying to change the way people are opening links on their computer. This small Mac OS X application gives you the option to choose which browser you'd like to open up any link with sans having to ever set a "default" browser.
In my case my default browser is Firefox, but it's not always the best solution. Sometimes I'm opening up a link for a site I know will work better in Safari or IE (like my work e-mail). With Choosy installed, clicking that link simply gives you a pop-up of whatever browsers you have installed--giving you complete control of what application should load.
The tool's real power is that it can be set to open a link in a browser you've already got running, or from one on your list of favorites. All of your installed browsers can be re-ordered with the ones you use the most front and center. In the example video (embedded below) you can see this comes in pretty handy when you've got close to a dozen installed on your machine.
Choosy Walk Through from George Brocklehurst on Vimeo.
Choosy is currently free and in beta. Upcoming features for the app include giving you the option to set specific domains to open in certain browsers, and multidisplay support.