Online Writing Labs (OWL)
There are many excellent resources on the web that can help you to fine-tune your language skills, but sifting through them in order to find the best can be a frustrating and unnecessary demand on your time.
The links below will take you to websites that are widely-acknowledged to be among the best.
It may look a bit dated, but this website receives around 30,000 hits per day. It was developed by American grammar enthusiast, Dr Charles Darling, and includes an index for identifying and diagnosing problems. The resources are interactive, but even more importantly, well-informed. Every-conceivable area of grammar and writing are covered, and the quizzes and tests are very good. While international students whose first language if not English would gain a lot from using this site, any native speaker of English would also benefit from exploring the resources.
In America, Online Writing Labs (OWLs) are quite common; so much so, in fact, that almost every US university has something akin to the original OWL site at Purdue University, to which the above hyperlink will take you. In the UK, higher education institutions are lagging behind in terms of the level of expectation and support that is available to students regarding language. Like the ‘Guide to Grammar and Writing’, all the resources are interactive and of a high quality.
If you find that you are not getting on with either the Purdue or Charles Darling site, this is a list of recommendations from Yale; a kind of ‘best of the web’ relating to writing and grammar. It includes recommended sites for first- and second-year undergraduates, sites for report writing, sites for research, and sites that are discipline-specific.