Pipes is a free online service that lets you remix popular feed types and create data mashups using a visual editor. You can use Pipes to run your own web projects, or publish and share your own web services without ever having to write a line of code.
It's fantastic -- Gmail for RSS. If Bloglines hadn't just made their only decent upgrade in months, I'd be switching. I still will if the Google people integrate some means of easily re-blogging to del.icio.us &c.
<access:restriction relationship="allow" /> and
deny to declare whether or not the feed can be re-published, made available to search etc.
I imagine there are many people syndicating "private" feeds through Bloglines and inadvertently making them public.