Maybe everyone knows this already, but in case not…
Put your cursor in the name of an interface (say, a Display interface nested in a GWT presenter) and press Ctrl-T. Eclipse shows you all the classes that implement the interface and you can then navigate directly to an implementing class. I frequently use this in combination with Ctrl+Alt+H to find out how a method gets called.
You can find all of my favorite keyboard shortcuts in my Eclipse Google notebook listed in the left sidebar.
