There is a wide range ages and abilities in the "elementary student" range. Thinking back, the best online activity that I used to engage elementary students was a simple "email pal" program with a grade 4-5 class. I connected with another elementary school with a grade 4-5 (split) class and had my students compose thoughtful and clear e-mail correspondence.
We emailed once a week every other week for the entire school term. The kids loved it and the program was a success. They really liked learning about other students in another school and while certainly simple, this core activity taught them many important skills.
From basic letter writing (intro, answers, questions, closing), to typing skills, to empathy, to reading, writing, grammar and much more, this was simple and effective.
For social studies I have used the pbskids site which has an arthur matching game for countries around the world. The kids loved it. The website is www.pbskids.org.
I find a lot of online activities for my students at linktolearning.ca - it has tons of links to websites that have educational activities and lesson plan websites.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.