The great thing about Del.icio.us is that you connect with sites chosen by others who have the same interests as you. When you click on the "saved by 5 other people" tag (the number varies), you get the webnames of those people, and the lists of sites bookmarked by them. Hence the social aspect of this resource. You can copy URLs of special interest from their lists. You can narrow your search by selecting only the "history" tag on somebody's list and getting even more specific hits. It really is a wonderful way to expand your own research. It's as if somebody else has done a lot of the work for you before you even start doing your homework.
I liked these new Lincoln sites so much, I added them to my Rollyo list. Then I moved the Rollyo search box to the top of my page, just under Lincoln's picture, which one person thought looked like Leonard Nimoy.
I also added three or four of these websites as new links on my page. And I'm going back to Del.icio.us to get more. What a great idea to have a simple button available at the top of the Explorer page, rather than scrolling through a "favorites" list each time you want to find something.
I hope others will check into my list and share some of my bookmarked sites. I see this as a powerful research tool, because the information retrieved seems more specific in nature than the average internet search, and the choices increase when new members join.