Cassini (Visual Studio development web server) by default enables directory browsing, how can I enable directory browsing on IIS Express by default? (I don't want to have a separate configuration for each project I have?
You should be able to use AppCmd.exe to manage IIS Express. Try this:
appcmd set config /section:directoryBrowse /enabled:true
More info on AppCmd.exe here: http://learn.iis.net/page.aspx/114/getting-started-with-appcmdexe