Desktop aggregators are great. They sit there all day, pinging away at sites, and as soon as they notice something new, they pop up little windows on your desktop, and let you read items. But what about when you go home from work? Or what about when you are on a trip? You get totally out of sync, and don't know what you've read and haven't read. You are enraged.
Feed on feeds is a Server-side RSS aggregator made of PHP. It can be used something like "Bloglines on your server".