Daily Writing Tips: http://www.dailywritingtips.com/
I'm too lazy to study English with textbooks, but to follow this tiny tips for English Writing is not a burden even for me. One article a day is just right for me to continue reading without delay. It's intriguing to know the difference of the questions raised by people learning English in different countries. Some of the questions are quite easy for Japanese because we take relatively through grammatical lessons at school, and some answers are really helpful to clear the usage of certain expressions. I do recommend you to subscribe to this daily mail or follow the articles with reader.