Tag Specific RSS Feed

I would like to have wordpress generate a RSS feed which would contain only posts that have the tag “facebook” in them.

So that I may post regularly to my blog, and have those posts with “facebook” in them pushed into a feed which is checked by facebook, and facebook will then import as a note.

This is similar to Ubuntu Planet, whereas people have regular blogs, but they have specific ubuntu tags which will place those specific posts on the aggregator.

Thank you!