I have used Scoopit as a quick way of putting a page of links for children to use for research before. Here are two examples for years 3/4:
Vikings : Vicious Vikings (used last term for our Invaders and settlers theme)
I have also started collecting ideas on Pinterest when a fellow student showed me her collection. These tend to be much more image based and as Pinterest is blocked in school, are usually for my own ideas. I started using it to gather ideas for my classroom, but it is particularly good for art (ideas for arts week themed around Diwali) and any sort of poster or display resource you could ever want!
For curriculum ideas, I collected pictures of maps and resources for our Around the World theme this term.