Excellent mechanics, grammar, usage, spelling (MUGS) site that allows you to work at your own pace and customize some of the content of the examples with sports, celebrities, music, etc.
Great place to work at your own PACE!
This is an amazing writing/grammar/reference resource you should be using ALL THE TIME! It can help you with thesis statements, organizing ideas, MUGS, and a bunch of other things -- the whole process. I'm gushing because it is AWESOME. Use it. NOW.