Any good sites to teach grammar?

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Hi there. I have realized since I do not read a lot these days, my writing skills are going downhill. I have some (what I think are) great ideas for books, but I am a bit afraid to write because I feel kind of illiterate. lol. Can anyone recommend some free tutoring sites for improving writing skills? Also I need to learn my parts of speech and diagramming. I never wanted to learn parts of speech when I was in school because I wrote well. Now for my stubbornness could kick myself! Thank you very much for any help you can lend me. I appreciate it very much!