If you’ve never played with Yahoo Pipes, you should. The innovative interface alone is worth it.
Here’s a simple yahoo pipes example: lets say that you have a blog that you want to syndicate differently to different audiences (for example we have a Tumblr blog and we want to exclude some of the content from the rss feed for use with facebook pages). The solution is simple; add a tag to posts that you want to exclude on tumblr and then use yahoo pipes to filter out those posts and generate a new RSS feed.
You can try it with your own Tumblr blog and tag.