This is not Ubuntu specific (as I no longer use Ubuntu) but will Docky ( http://wiki.go-docky.com/index.php?title=Welcome_to_the_Docky_wiki ) which is in the Ubuntu repos run on gnome shell? I know it requires compositing which is provided by mutter.
"A picture is worth a thousand words..."
Picture shows Docky running in Gnome-Shell in 11.10
Mutter describes itself as a "Clutter based compositing GTK2 Window Manager" (man page). I understand that one of the goals of the Docky devs was to have Docky work with Gnome Shell, but can't remember where I read that. Anyway, it ought to run just fine under Gnome Shell.
However, Docky (which is in the Ubuntu repos) will work with almost any Desktop environment, including GNOME Shell. It also works without compositing (technically), but will just have problems drawing itself.