English Writing Software

I was wondering if anyone knows of a Mac application that assists individuals with writing. I am a college student and always wondered weather or not there is such a program that can help me out while busting out endless amounts of papers. Any help would be great!

What kind of features are you looking for? For layout purposes, I find Apple Pages to do very well when trying to implement your college's layout specifications in your term papers.

Basically a program that extensively proof-reads your work in more detail compared to Microsoft word, like spell check and fragment sentence checker.