Is there a good place to power level in Dragon Age origins?

Answer 1

No, Dragon Age: Origins doesn't have respawning mobs, so the best way to level up is simply to do as many quests as possible and explore.

Answer 2

You might find this tutorial useful:

http://roosterteeth.com/archive/?id=944

I find the game is more rewarding if you don't use this method and level normally. But going around beating down everyone is fun too!