The Publishing Training Centre runs a Grammar at Work distance learning course, aimed primarily at professionals but I would say applicable to most of us, and you can run a self-assessment test on their website by going to http://www.train4publishing.co.uk/elearning/gquiz1
If you thought your grammar was pretty good, one or two questions might make you think again! (Or not, maybe it's just me..)
The link for the actual course is: http://www.train4publishing.co.uk/elearning/gaw
