Flexpaper is an open source document viewer--and it is beautiful. The Flexpaper API lets you incorporate your publications into other applications. Flexpaper works on virtually any device and is, no surprise here, flexible. It can display in HTML, HTML5, Adobe Flash or any combination of these.
Mimeo.com just launched a new area to support its family of APIs, print marketplaces and enterprise print integration tools. Developers can build applications that offer print-on-demand services, using the Mimeo Connect Cloud Print API. Mimeo.com has long had a SOAP API, but has recently built an easier-to-use RESTful API for developers.