Is there a legimate music download site - like iTunes, etc - that people find good for whatever-their-personal-definition-of-folk-music?

I looked at iTunes when it was it was first available in the UK and have just looked again, and there is very little of what I would call folk (Example test: How many Watersons/Carthy songs does it hold?)

So, is there a legal, buy-a-track site people like?