It would be really nice to have tags for questions listed in the body (or title) of RSS items. Quite often it's impossible to determine technology, programming language, etc. from body text itself.
Well, it already is -- for example the feed for this very question contains:
Is there something else you're looking for?
I have written a small application called stack2rss which converts API requests to RSS feeds.
It also includes the tags in feeds for questions.
Here is an example:
It returns all questions tagged