I recently discovered two sites which are trying to develop markets for digital content, but on rather different lines.
RedPaper aims "to create a place on the Internet where any type of digital content no mater how abstract could be bought and sold by anyone interested in transacting it." It is supported by a range of venture capital bodies, but also by Adobe. They have adopted a micro-pament approach modelled on Paypal - in fact if you make any money it is transferred to your Paypal account. I've so far made the huge sum of 85c! I think their sell it cheap in quantity philosophy is probably the right one but in the long run it doesn't seem sustainable at 10c a photo - which is all I've had (unless the user base expands substantially). Bearing in mind Corbis will sell images at around $4-5, then probably RedPaper needs to be selling at around $0.75 - $1.50 per photo for people to judge it worthwhile uploading. I'm willing to hang on for a while but at those prices I won't be uploading anything more than a taste of what I have available. I'm also not sure yet how willing the general web user is to use systems like Paypal. They have to become pretty much ubiquitous and widely trusted to have an impact.
I haven't worked out in my own mind what a comparable figure would be for poetry or other fiction. I sold one short short for 10c and about four pages from the NaNoWriMo work I did for 15c - which doesn't even cover the time spent in uploading it. None of my poetry has sold - even at 10c a time. One problem is that you are to a degree buying a pig in a poke there is no way to sample what is on offer before you buy. At 10c a time that shouldn't be an issue but so far...
The other site is Lulu which I haven't investigated closely. I'm going to try it as a comparison with Redpaper, but one immediate problem is that anything you sell is on a royalty free basis so allowing further use. In truth I'm not sure that anything else is enforceable but its too early to give up.
Give them both a look.