I think you have a great site as well. This is not legal advice, but you may want to ask for permission before mashing someone`s RSS feed into a composite feed. I don`t think that displaying headlines is inappropriate, but many RSS readers like Grazr.com can allow for full reading of people`s RSS content without going to their site, which is often considered infringement (especially if it happens on sites that sell advertising). Think of it as putting someone else`s site in a little box inside of another site.
You could ask for permission by first setting up a test page for site owners to check out, just to be sure that people understand what you are doing.
Widgetbox.com has a nice interface for customizing and displaying RSS headlines. One question I would have is whether it is clear where the RSS headline is coming from. People will not be happy if their headline just appears randomly without the name of their site.
Hope that helps!
Andrew Darlow, Consultant & Editor
The Imaging Buffet
Author, 301 Inkjet Tips and Techniques: An Essential Printing Resource for Photographers - InkjetTips.com