I'm curious to see if I find this useful. The product's not ready yet, but I've signed up to get it when it is. It's an IE and FireFix plugin that allows you to snapshot the web page you're on (they call it "notarizing") so that you can get back to it later.
Sounds like bookmarking, right? But it can save the state of the page you're on, whereas bookmarking can't always do that. An example they demo uses Google Maps. As you browse different geographic areas in Google Maps, watch the url in your browser. It doesn't change. So if you were to bookmark the page, the bookmark wouldn't take you back to the page as it was when you bookmarked it (yes, I know that Google provides you a way to do that - this is just an example). But the iterasi plugin will save the page, just as it was when you were looking at it, on their server, allowing you to look at it again at a later time.
Their service will also allow you to schedule automatic, periodic snapshots of pages you choose. So you could monitor how a page changes over time.
Again, I look forward to seeing if this ends up being useful to me.