You can watch season one and season two on Hulu, (series premire: http://www.hulu.com/watch/78885/merlin-the-dragons-call#x-0,vepisode,1,0)
and some of season 3 can be found on youtube. Season 3 ended a few weeks ago in the US.
EDIT: ALTHOUGH, THE SERIES PREMIERE itself is not as good as the rest of the series itself is
What I love about the show is the relationship between young Merlin and young Arthur, Merlin's his servant and friend, and all the action, and how the legend of Excalibur, and Guinevere/Arthur/Lancelot etc plays out in the show, all the creatures, the foes, it's like my top show right now since Lost.
Originally Posted by StevenGlansberg
Co-sign the Arrested Development.
Yeah, Arrested Development is a really funny show, you should watch that too
Originally Posted by MojoCrunch
That was a really good show too, loved it although I feel like it might drag on for you, from what I remember, besides the growing relationship between Xena and Gabrielle, many of the first seasons were about having to save the day, the really good plot involved story stuff came later, but no doubt about it, it was a good show bottom line with all the mythology, the action, the gods(Aries the god of war, Discord goddess of Chaos, etc etc), Xena's past, the Amazons, etc etc.