As mentioned elsewhere, if you run your own Wordpress, there are good plugins (such as Social Network Auto Poster) that will post to DW and all the other locations. This does not work with Wordpress.com, because they don't let you pick your own plugins very much. They'll do Twitter and Facebook, but not DW. But not everyone can or wants to run their own install of Wordpress.

For those looking to start with DW at the center, you might also check out Zapier. They have an RSS to Facebook and RSS to Twitter flow. They're pretty much the Pepsi to IFTTT's Coke.