Just to write this down somewhere before I forget it again...
It's easy to make those Gnome pop-up notifications from the command line
notify-send 'Venture Bros' 'Go Team Venture!'
perl -MGtk2::Notify=-init,Venture -e 'Gtk2::Notify->new( "Venture Bros", "Go Team Venture!")->show'
python -c 'import pynotify; pynotify.init("Venture"); pynotify.Notification("Venture Bros", "Go Team Venture!").show()'
All three of these will give
for a few seconds.
Apparently, you can do it from Ruby too, but I haven't got that installed.
perl -MDesktop::Notify -e 'Desktop::Notify->new( app_name => "Venture")->create(summary => "Venture Bros", body => "Go Team Venture!")->show'
in Xfce and
in LXDE. These match our desktop perfectly, but they show up in the center of the screen and must be dismissed by hand. That's not always what we want. The libnotify (and growl, I think) notifications show up in the corner, have no buttons or window dressing, and dismiss themselves.
ETA (21 Dec 2011): I bet the anonymous commenter mentioned above is a KDE user. I just tried both the Gtk2::Notify and the Desktop::Notify one-liners above and they give the same result in KDE
I'm not sure if KDE is handing off to libnotify, handing off to dbus, or doing its own notification. In any case, Desktop::Notify does seem to be a nice option for KDE users. On the other hand, Gtk2::Notify looks exactly the same, so I'm not sure what's "jarring" about it.