If you use Google Reader as your RSS newsfeed aggregator, take a look at Lifehacker's How to Declutter and Streamline Your Google Reader Inbox post.
Get tips on how to...
- delete unnecessary feeds using the Your Stuff -> Trends tool to root out inactive blogs
- adopt a prioritized folder structure based on how important a feed is to you
- customize your subscriptions to WordPress blogs with tags & categories
If you don't yet use Google Reader, watch this short video introduction & overview to get started!