Trailers or promotion videos can be very effective when done right and the Java community has been pretty good at it IMO.
The latest ones are short teasers coming from the JavaBin folks to promote their very fine JavaZone conference in Oslo, Norway in September (celebrating their 10th anniversary). Update: the entire trailer is now available.
Previous videos include Lady java and Java 4 Ever (must see if you somehow missed them). The inspiration for these may have come from the JavaPolis (now Devoxx) 2006 "There are better ways to meet your idols" trailer. IIRC, James Gosling was quoted saying "This is sick, I love it!". Your mileage may vary ;)
Sun Microsystems also used to make some "promotion" videos. Here's a selection.