I used to use the RSS feed from space.com that Jamie Zawinski made (they’re not cool enough to have their own). It was ok, but not a lot of traffic, and some pretty boring news.
This weekend I found spaceref.com. Wow. It has a great combination of completness, diversity, and categorization. For example, there are RSS feeds specifically for news about Mercury, Saturn, Mars, and the ISS. They actually give regular reports, several per week, regardless of whether planet shattering news is found or not.
If you’re into space, it’s a must watch on the rss feeds. If you’re mildly interested, just watch me re-post the cool stuff. 🙂