MUGEN Ultimate Tutorial (YouTube)
MUGEN may be getting a bit old, but modding definitely keeps it fun to this day. There are many tutorials out there, but I found this one to be a little better than the usual finds on YouTube. The tutorial is in four parts and covers basically anything important you could possibly want to do with MUGEN and a beginner. You will find all four videos after the break.
Wikipedia: M.U.G.E.N is a free 2D fighting game engine designed by Elecbyte, written in C with the Allegro library. The engine was originally released in July 17, 1999.
Thanks “uroz23″ for putting a great instruction series out there.