this was a new post today http://arxiv.org/astro-ph/0401244 it is still just a germinal idea remember in 1998 type IA supernovae were used as a standard candle and the luminosity-distances of them at various redshifts pointed to the existence of dark energy or cosmological constant Lambda (add your own name for it here). well so far not all that many GRB have been observed (around 30 have had their redshifts measured) but they cluster around the same inferred energy on the order of several 1050 erg, these authors say that is 1043 joule or, in planck terms, on the order of 1034 natural units of energy, that seems like a lot of energy to be concentrated in a brief flash of gamma rays---I wonder if I understand them right. In any case, these people suggest that once there is a large dataset and 300 GRB or 1000 GRB have been observed then, since they all have about the same energy you could use them as standard candles and compare the numbers of them at various distances in a universe with dark energy there would be fewer close by and more further away, compared to a universe with only dark (and ordinary) matter. It is a catchy idea. The thing with Type IA supernovae was that because of what causes them they all have just about the same energy. So they work as standard candles for judging distances. So could the same thing be done, but over larger distances, using GRB as standard candles. I cant tell if it is a sensible proposal, but I like the sound of it.