I mocked up where I want to go next with the beautiful river stuff.  

http://scripting.com/images/2011/02/10/nextStepInRivers.gif 

All I did was split the page horizontally and add a box where I can add a message to my output stream. I already have the back-end for this completed and debugged. I have a UI, but it's a pretty ugly HTML form. The goal is to integrate the two. 

Here's a screen shot of the form I'm actually using, that's functional.  

http://scripting.com/images/2011/02/10/messageEditor.gif 

Notes about the editor. 

1. The pop-up menu says which feed the item goes to. I can manage more than one. 

2. The full link is entered in its own box 

3. There's a link to the feed (the white-on-orange XML icon). 

4. There's a link that pings TwitterFeed saying the feed has updated.  

5. The number is a count of the characters in the box. I'm going to allow you to set a limit and it will turn red whne you go over the limit. (Not implemented yet.) 

There's also a message area, to the right of the popup-menu, but since there is no message being displayed you can't see it. This is for confirmation messages like "Updated feed" or "Successfully pinged TwitterFeed." 

I see this evolving quite a bit, but this is the core functionality. With these two pieces integrated, there will be the equivalent of a Twitter client that only uses RSS to communicate. 

Cross-posted on the River of News list.