
I've talked about Road to Grammar before, and I've still no idea who's behind the site. However, I thought I'd mention it again because it has some really good resources for both students and teachers, yet also seems to be something of a well-kept secret.
As the name suggests the main focus is on grammar, with 365 grammar quizzes linked to explanatory notes. But there's plenty of other useful stuff such as games and downloads. I particularly liked the Flash-based game Fluent, which allows 2 students to play. Meanwhile, the Downloads section has some great PDFs including an e-book with 25 factoids for EFL teachers and another with 100 conversation questions.
The only thing I did find a bit annoying was the navigation, as there's often no link back to the homepage from within the site. This could easily be solved by adding a link to the header.

FOOTNOTE
I got an email from the creator of Road to Grammar. Here's what he told me:
My name is Emile Alexander Dodds and I am currently working for an e-learning company in Malaysia. I am originally from Scotland and I have a background in TEFL and about 15 years of experience in teaching, training and also e-learning. I started roadtogrammar.com as a hobby, basically, and as a place to put useful activities for my own students. I did absolutely everything on the site myself. I'm a self-trained programmer. The roadtogrammar site has been around for about 5 years now and I get around 600 or so visitors a day.
Emile has plans to expand the site and make some of the activities accessible on mobile devices. I look forward to seeing the results.