Antiproton Annihilation Propulsion
I added a new link to Starship Generations describing the possibility of using annihilation decay particles as a high thrust, high specific impulse propellant. It is not recent, but how often do you hear about this sort of work anyways? It is probably a black military project.
http://www.geocities.com/womplex_oo1/StarshipGenerations.html<Starship Generations