Lessonstream.org currently offers a small but varied and interesting collection of free English lessons, divided by ability levels (A1 elementary to C1 advanced), listed according to topic, language aim, learner type and lesson time. Each lesson starts with images or a video, preparation tasks, text prompts and then the lesson plan.
New lessons are only added slowly, approximately once a month, but there are a little over 70 ready-made lessons on the site waiting for you. The materials are complete and widely varied in subject, so you're certain to find a few of interest to you and your students, whoever they are!
There are lessons for young learners, teens and adults and the lessons are all free.