As I mentioned before, Fotomoto seems like a really great service which takes pretty close to zero effort to set up (there is a great Worpress plugin), and it costs £0.00 to sign up to and use.
I have enabled it for all full size photos on my web site
The only thing I am having difficulty with is what to charge and what currency to use for a download with commercial use license. Going by previous experience, I'll be lucky to sell more than one photo a month anyway, but for some reason in the past most of my sales have been to the UK in Sterling - so that is the currency I have chosen. Since most of the full size images on my site are under 1 Mega Pixel, I've decided the most I could possibly charge for them is £20. So this is what I am starting out with. Once I've had 100,000 visits and no sales, I'll maybe look at this again, but I still don't envisage photo sales earnings being more than 5% of AdSense earnings.
By the way, Fotomoto do give you the option of specifying an FTP repository where they can pick up high resolution versions of your images to sell on your behalf which is a great idea, but I don't think I'd sell enough photos to justify the time an expense in setting this up (It may be a different story if I was a first rate photographer with really amazing images like Captain Kimo with his
HDR Photos.