Is it possible to have a particular 10.4 widget permanently docked on my desktop?

Yes. It is quite easy.

First, switch to Devmode by entering the following command into the terminal:
defaults write devmode YES

Log out and log back in again, and you will be able to drag as many widgets to the desktop by holding down F12, opening a new widget, and then releasing F12.

The widget will be on the desktop every time you log in, until you go into the dashboard to remove it.

Oh and one more thing. You have to drag the widget back to the dashboard, the same way you got it onto the desktop, to be able to remove the widget.

I mean.. wow. Good info.

Nah... I just read it out of one of my old Macworld issues :D

Thanks for the tip :) I'm actually going to go ahead and move this thread to the Tips 'n' Tweaks forum :)

I assume I need to do:
defaults write devmode NO

to get back into normal mode?

That would be the logical assumption :)