This may be something that most people already know, but it took me by surprise. I was looking at the contents of one of my project's directories in the Navigator window, and inadvertently double-clicked on a Word document. Guess what happened? That's right, the document opened in Word, inside an Eclipse editor window.
Pretty cool, actually. Now I don't even have to leave my favourite environment to edit Word docs. Not surprisingly it works with Excel and Powerpoint files as well. Must be an OLE thing.