I was looking up something this morning when I came across this website, and fell in love.
http://public.wsu.edu/~brians/errors/errors.html#errors
It's designed for profession writers, but if there's anything you've ever wanted to know about the English language this is the place to find it out. I discovered several things that I didn't know, which doesn't surprise me. There are actually a lot of things here that are fun.
For example: I've always known that "data" is plural, and one of them is a "datum". What I didn't know is that "data" has been popularly used as a singular for so long that these days some scientists have coined "datums" as a plural! To me that is just weird.
Anyway, if the study of your own language, or a foreign one to you foreigners, has ever interested you at all, this could be interesting as well as helpful. To those of you not so inclined, move along, nothing to see here.