After a little digging, I found that Yahoo
not only offers the news category feeds I
noted above, but also has a news search feed
in beta.

Check it out:

http://search.news.yahoo.com/usns/ynsearch/categories/47/index.html?p=your-keyword-here

Just substitute your keyword(s) where it says your-keyword-here above. For a phrase, be sure to use the + sign. Examples:

one word p=dog
two words p=dog+food
exact phrase p="dog%20food" (%20 is a space, quotes required)

This is the equivalent of the gnews script
for Yahoo, except Yahoo is providing it
directly. Hope they keep it!

Best,
Jeff