I use Evernote to organize research, notes, email chains, etc. You can put each item into the corresponding project folder, then tag it – which makes it easy to find things lately. I tag next tasks with “urgent” so I can do a quick search in the morning and figure out what needs to be taken care of.
I know you can share Evernote folders, which could make it useful for collaboration, as well. I’ve never tried using it that way, though.