If you know what the Semantic Web is all about and like the idea, then you'll love Twine. Just check their tour!

I've got 5 invites - but if you want one you'll have to motivate why you should get it! No extreme amounts of text is required, just take a look at what I, and a few others, wrote to get an invite:

http://www.thinkartificial.org/web/twine-think-artificial-invitations/#more-766 (It's a little bit down on the page)

I've 25 invites now. More info in my personal forum: http://www.tangler.com/forum/nsof/topic/42219