Advanced Gnome Menu (AGM)

Advanced Gnome Menu (or AGM) is a combination between a menu and a dock. Even though the word 'Gnome' is in it's name, it will soon also work with KDE and Xfce (or it could already work, I can't test this as I only have Gnome installed).

It supports themes, plugins (actually this is what's displayed in it: the usual gnome menu, bookmarks, favorite apps, etc), transparency, etc.