In the UK I think most of us buy a professional / public indemnity bundle from Hiscox, which costs a couple of hundred gbp or thereabouts. It's normally a contractual obligation.
Ah, well in the UK you have it much easier with the existence of the NHS, whether or not it covers all of your needs. As I'm sure you know, in the US if you don't have insurance, you don't really have much of anything--and due to the tax advantage setup to get insurance through one's employer, self-employed people get hit really hard with insurance.
