In describing RSS and aggregation to my students, I came up with a useful metaphor. I'm guessing I've seen pieces of this out in the web, such as the River of News metaphor for aggregators. If you use it in person, make sure to add lots of over-acting to demonstrate the point. And let me know how it works for you.
Reading a weblog is like jumping into a stream. You get into your swim suit and hop in. Each stream has its own character with different creatures swimming in and around it; hot or cold water; fast or slow; sandy or muddy or rocky. When you are done, you jump out, dry off and hope that you've seen something new since your last visit.
This probably isn't too much of a hassle, if you are just reading a few weblogs. But as your interest grows or your circle of friends grows, there are more and more streams to find. And for each one, you need to get into your swim suit, swim around, climb out, dry off and get dressed. All that to find out that the stream was a little slow this week and there weren't any changes.
Wouldn't it be better if you could set up a personal canal or pipeline, where only the streams you want to visit are collected in a larger stream? Then, you could hop into that stream see what is new and hop out without having to head off to the next one. And let's make sure it is personal, since you are going to want to add that purple stream to your canal, and I want that one full of lobsters.
Well, it turns out that nearly every weblog offers a "stream" of information from the website. This is called a web feed or an RSS feed. These streams can be fed through any number of devices, but the one like a personal canal is an aggregator (or news reader).
So, as you find waters that you like, add them to your personal canal of news.
There are some drawbacks, of course. You lose the unique ecology of the individual websites, so if you are really interested in the rocks and trees the stream flows through, then it's better to visit the stream directly. But, if you are interested in the water, then collecting it in one place shouldn't be as much of a problem. In some cases, it isn't possible to pick up a full stream: some stream-minders prefer to only provide part of their water to a canal. They want you to come and visit their waters, and provide only a taste.