When I emailed a colleague in Chicago about the challenges of teaching students grammar, he told me to check out a site called Noredink.com. He hadn't used it himself, but had heard many endorsements.
I have been a faithful user of the site for about a year now. While perhaps students will never develop a love of grammar, the staff of Noredink has found a way to make it painless and even fun. Also, their instructional materials are clear and concise.
How do they do it?
Students answer a series of questions about their friends, hobbies, favorite music and t.v. shows. Then the site uses that information to create sentences. Students practice and then are assessed using sentences that say things like: "Homer Simpson love to eat cake, apples, and doughnuts."
However, like with all websites, the role of the instructor is critical. First I introduce a concept, then students practice it on the web site, and lastly their assessment is also through Noredink.
I highly recommend giving it a shot. The level that I use is free.