Futher emphasising what Cinqueta has just said.
Recently, in the news a human stem cell trial has been given the go ahead in america, on patients with spinal injuries. Though it'll be decades before stem cells become widely used, this is a pretty good breakthrough. <-- this was quite big news so just a basic google will link you to stuff
Also in the news, recently, the idea of using stem cells to create "new livers" for patients who need organ transplants (due to the shortage) is being looked at. They can either be used, with some form of structural cellular support as a backbone, to create whole livers or create lines of liver cells which can form a better version of dialysis. I.e. the cells do a better job of removing the toxins etc... (I think that was it. Not sure though).
Big no-no regarding stem cells is the fact that the very useful form (embroynic) comes directly from foetuses, thus you're, in essence, taking away a life. This then goes into the whole pro-life argument which is very easily googlable.