The Hemingway app is fantastic for helping cut down the number of words in a given document. It's also helpful for trimming thesis statements down to the essentials, or for clarifying content in general.
http://www.hemingwayapp.com/
The University of Chicago's list of grammar resources contains several guides and free online programs to help clean up grammar or answer quick questions.
http://writing-program.uchicago.edu/resources/grammar.htm
When you want to be entertained and also learn something in the process (mostly on the creative writing front), check out the How to Write Badly Well site. "Have everything happen suddenly" is always good.
http://writebadlywell.blogspot.com/
Again on the creative writing side of things, if you feel like you're suffering from writer's block, you may want to check out this list of 365 Creative Writing Prompts from ThinkWritten. It can be good for analytical writing, too-- sometimes you just need to get some words on the paper and free up your brain before you can get going on that paper.
http://thinkwritten.com/365-creative-writing-prompts/
In case your teacher really wants you to put an assignment in MLA format, but you can't remember what all of the guidelines are, here's a summary from the Purdue OWL of the 2016 MLA Handbook.
http://thinkwritten.com/365-creative-writing-prompts/