Grammarly is aimed at ‘anyone who writes and wants to improve his or her writing – students, bloggers, writers, and professionals’.
It’s more thorough than your typical checker, scanning for ‘more than 150 common and advanced grammar rules’. It also looks at punctuation and contextual spelling (such as confusion over to, too or two). It even checks for plagiarism and creates references if it considers the text has been lifted.
At present, the free version has limited features but still worth a try, there is an integrated MS Office version (also free). Unfortunately, the premium version comes at a cost that’s currently not covered by SHU, but might be in the near future. The chrome extension or the desktop apps version can be helpful when writing assignments or emails.