Grammarly is a free resource which you can add to your browser or download. They do have a paid version which I am currently testing out. I have to admit that I do like it. It's not a cure-all for bad grammar, but it does help clean things up for those of us who are grammatically challenged.
In my case, it's helped immensely with passive voice. I point that out because I know it's at the end of my last paragraph.
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