Over the years, web based applications have made it easier for people to create and share content on the web. Examples include:
- usenet: text
- blogs: html
- Flickr: images
- YouTube: videos
There is definitely a progression in the richness of the media being created but they all have one thing in common: they are all passive. You can look at an image but it will not interact with you nor will it change over time.
There is however a new category of active content emerging. The earliest examples I can think of are greasemonkey scripts. These are active in the sense that they operate on other content and their output therefore will change in different situations and over time. Pipes is another example of enabling users to create active content. A Pipe is an instruction set for how to operate on feeds. Its output will change over time based on its inputs.