In Mac OS X there is a handy open command that opens the target file or directory in the default GUI application meant for it:
open /usr/local/share
will bring up a Finder window with the /usr/local/share directory open in it (BTW I don't know of any other way to open this particular directory in Finder) and
open ~/Desktop/example.jpg
will bring up a Preview window displaying the example.jpg file located on the current user's desktop.
Is there an equivalent in the GNU/Linux world?