I've looked around for other listing marketplaces for writers. The biggest and probably the best is Constant Content. I mentioned it below, but it's worth describing in greater depth.
The site clearly gets a lot of visitors, many of whom are keen to buy good content. You can also choose which kind of rights you are offering to the buyer. The site does take a substantial commission of 35% on each sale however. I've also read a few complaints about how picky they are about grammar and spelling from some disgruntled folk. But surely that's a good thing in the end. You just have to go through each article with a fine tooth comb before submitting it to make absolutely sure that it's perfect.
There seem to be only two other sites of this kind. One is called Daily Article. This looks pretty good. And from what I've read it takes a 20% cut. There does seem to be pretty good quality control, however I get the impression that it's not quite as stringent as Constant Content.
Unlike that site, however, you don't have any choice about what kind of rights you're selling. You basically just hand over the article completely to whoever buys it. And they can basically do whatever they want with it.
There's another site called Article Sale. This one takes no commission, and seems to get its entire income from serving ads. Like Article Sale, you sign over all your rights with each purchase. There doesn't seem to be any quality control, and after reading some of the negative reviews of various authors, it's clear that a few are just uploading duplicate content.
That said, people are clearly buying stuff from there. And it could be just the place to sell short blog post type articles for 4 or 5 bucks a pop. I'd imagine that you could end up with some regular customers pretty easily.