Michael Frumin and Michal Migurski, the development team behind reBlog are showing it off. At first glance, reBlog looks like an online feedreader (with a nice interface). The difference is that reBlog is aimed at using the information in feeds rather than just reading it. You can easily republish information, archive it, tag it, add comments, and so on.
In addition, a plugin architecture let's programmers and developers add new features to the RSS processing chain and customize it to specific uses. For example, you could subscribe to a feed that contains items from eBay and then use the plugin to connect to eBay and pull down additional information about the item (not included in the feed) using the eBay API.
reBlog is in PHP and can be loaded on your own server. There are Wordpress and Movabletype plugins that interface with reBlog. This allows easy reuse of content in feeds. GardenVoices from iVillage is an example of a reBlog.
There are questions of copyright and re-use that the tool doesn't answer. Still this is not splogging software that just republishes content without attribution. In the end, there's a human in the loop; making editorial choices, as it were.