After a book or a magazine goes out of print, it may happen that the content within it--the articles and photographs--can be worth more as pieces and parts than as a finished work. Blish is a service that will part out content and sell it in little pieces. It is the perfect example of a long-tail marketplace--it sells a lot of content that will be of great interest to a small number of people.
Blish is also a more general content market. You can take anything that can be transmitted over the Net and sell it on the service. Blish handles the mechanics of each transaction. There are, of course, plenty of other content marketplaces, such as Lulu, which will custom-publish books (on actual paper), and Digital Railroad, a new site for professional photographers. Smart content creators will use any and all storefronts available. With digital content, there's no real harm in distributing content to multiple markets.
Blish's angle, though, is interesting. If you feed the company your content archives (usually, a collection of PDFs), the company will deconstruct the data for you and sell it in parts. The strategy is working for some publishers already. Twenty percent of Blish's sales are woodworking plans that previously ran in magazines.
What's missing right now is the capability to create private-label versions of Blish so that publishers can incorporate Blish stores into their own sites, or at least direct their readers to Blish ministores that carry their branding.
If you're looking to acquire content--a legal form, a deck plan, a photo or a drawing, or a royalty-free music clip or a video--well, honestly, there are already markets for what you need. But also check out Blish. If the company can help publishers take finished works and turn each of them into thousands of microproducts, it could become a great junkyard of content. And I mean that in a good way.