This is exactly what I was looking for. Thank you, Isaac Pessoa and zspotter! I'm using Xfce on Arch, and in the spirit of keeping it minimal, I didn't want to resort to installing Compiz.
I'm not sure if this would or has happened to anyone else, but I noticed something pretty strange: The panel I set up to be the workspace indicator was configured to show 3 rows (I have 9 desktops). It was set to be about the same size as what you'd get in Ubuntu (about 3x6 inches). However, it would only show one row until I right-clicked the panel and selected properties (which, to be clear, was to display the properties window of the workspace-switcher). The fix was to remove the workspace-switcher that was on another panel.
Also, in order to change how long the workspace-indicator panel displays before it autohides again, you'll need to add this to your .gtkrc-2.0 file:
# Time in miliseconds before the panel will unhide on an enter event
XfcePanelWindow::popup-delay = 225
# Time in miliseconds before the panel will hide on a leave event
XfcePanelWindow::popdown-delay = 350
# Size of autohide window in pixels
XfcePanelWindow::autohide-size = 3
class "XfcePanelWindow" style "xfce-panel-window-style"
In my case, since I'm on Arch, the gtkrc-2.0 file doesn't exist. I had to add that to the gtkrc file in my ~/.themes/[theme name here] directory.
Change the popup-delay and popdown-delay to your liking. For some strange reason, I had to set the values at about half of what I wanted them to be. Probably has something to do with wschanged executing the script.
If you want to place a panel in the middle of your screen showing a grid of workspaces, (similar to Ubuntu) you'll need to set that panel's alpha (under the appearance tab in the panel preferences) all the way down. That way you won't see a small bar on top of all your windows. Setting the autohide-size value to 1 will make it almost impossible for that panel to show by accident.
One last thing: if the cursor happens to be on top of the panel when you're switching workspaces, it will randomly show a tool tip and I have to move the cursor off of the panel to get it to hide again. Not a big deal though.
EDIT: I used zspotter's fix for this.
EDIT: I just noticed that scrolling the mouse while focused on the desktop will switch workspaces (using zspotter's fix). Nice!
EDIT: This causes my notification popus (i.e. when using volume keys, etc.) to appear in the wrong place. Specifically, when using the options top-left or top-right, the notifications appear in middle-left or middle-right. I don't have osd-notify installed -- just xfce4-notifyd. Everything in settings appeared to be correct. When I removed the panel and took wschanged off the applications auto-start list, problem was corrected..