The "Countdown" screenlet posted at www.gnome-look.org has a serious memory leak. If you leave the screenlet running for any decent length of time it will eat up all your RAM (kinda like Vista, eh?). The problem is due to the "draw_text" method in CountdownScreenlet.py calling ctx.create_layout() every time the method is called. By creating the layout only when needed outside of that method the memory problem goes away.
You can grab it here: CountdownScreenlet-0.3.tar.gz