You would think I have never played Half-Life before with how excited I got when I saw this trailer.  Black Mesa Source is HL1 with a full conversion to Source Engine graphics.  Valve released HL1: Source, but it pretty much used the same graphics as the original Half-Life Engine.  It looks like the development team is going to be releasing this toward the end of 2009.  I can only hope they release it on time.  Behold!