You may be interested in a course available at https://www.edx.org/ You can select to pay for it to get a credit, or you can audit it for free.
The course is Write101x: English Grammar and Style, and information on it can be found at https://www.edx.org/course/uqx/uqx-write101x-english-grammar-style-1766#.VCGYwBajKSo
It started yesterday, and runs 9 weeks, with 4 hours of your time needed each week. I signed up to audit it, and so far I'm very pleased with what I see.
