Constant-Content is actually the topic of a future post since it’s a very special class of document reuse. There’s no doubt that sites like it support document reuse. They allow you to purchase unique content outright usually for publication purposes (such as your personal blog) — without the need to tailor whatsoever. Reusing documents in this fashion is by far the most efficient form of reuse — kind of like content on-demand.

Just to clarify the scope of the list above, it’s focused on sites that offer access to pre-made document templates or completed document samples to support some sort of process/activity/task that we carry out on a recurring basis in our personal (e.g., sending out X-mas cards) or professional lives (e.g., project management).