Wow, a webcomic just turned me on to the simple wikipedia and I have been blown away. It's like wikipedia, only not for people who are already rocket scientists.
Sure, it may be lacking some detail, but if there's a really complex subject you just want to learn the basics about, simple wikipedia is the way to go. Take, for example, the entry on the large hadron collider:
The Large Hadron Collider (LHC) is the world's biggest and highest-energy particle accelerator, used to make some very small things called particles hit each other.There's more info than just that in the entry, but how much more do regular folks need to know?
I strongly recommend everyone give this site a look.
p.s. In case you were wondering, here's the comic that inspired this post: