mmmm... Del-icio-us?
i checked out del.icio.us and found it to be slightly similar to rollyo in the way that you can customize and narrow down which websites/blogs are drawn from, however de.licio.us is more like a portable bookmarking site that allowes you to have favourite webpages available to you at any computer.
in a way it also combines the concept of google trends - where it shows you the popularity or how many other users have linked to particular sites.
i'm unsure if this tool would be the most useful for research. in some ways though it may make searching more efficient and succinct. hrmmm