LexiPtarmigan is a program that randomly selects words out of a very large dictionary and displays them. The standard one is here, and the variants below have alterations in the look of the page or the speed with which the words are displayed.
synchronous*small screen (smaller, denser font)
*green on green (in your browser's default font, also set up for smaller screens)
*Here's a slow one to leave running all day.