Oftentimes Wikipedia can provide a handy overview of a topic or an idea which helps me orient myself in my thinking about it. By contrast, ye olde Encyclopedia Britannica was verbose, rambling, and not well-organized for a clear overview. Just my opinion, of course.
The old one-volume Columbia Encyclopedia did that better. I relied on it when I was young.
Anyway, two recent Wikis that I used:
The Idea of Progress
Scientism