While my knowledge of how to use the English language is extremely solid, there are things that I don't know and have to look up. Sometimes, it's something that I know, I just don't know why I know it, so to explain it properly I do some research.
I thought I'd give you some of the links that I use to help get my usage straight.
www.wsu.edu/~brians/errors/errors.html - an encycolpediac repository of trouble words and concepts.
www.hotforwords.com/ - the origin and use of words presented by an extremely attractive Russian etymologist.
www.youtube.com/results - a collection of Schoolhouse Rock videos on grammar. I've posted the link before, but it's worth posting again.
www.dictionary.com - for all your definition needs. It even includes audio files for how to pronounce the words; your ink and paper dictionary can't do THAT!
Do you have any favourite language usage websites or podcasts? Share them with the class in the comments.