Synerge is a part of a site system known as the HelpWeb for Students - for more info, click the button right
Virtual High School: a more professional, paid version of synerge. compatible with Ontario curriculum
Khan Academy is a very useful tool which guides you through various subjects, notably mathematics and science, via video tutorials, text based descriptions, and problem based learning (they give you automated quizzes and tests). This software is web based, and free. An account is not necessary, but is recommended to track progress
Note: Khan Academy is generally used for maths and science, however it does have course modules in the Arts and Humanities, English Language Arts, Computer Science, and Economics.
Also note that certain types of courses, like English, are only applicable for certain grades: E.g, English Language Arts are only available grades 1-9
Note: SparkNotes is generally used for literature (ELA), however it does have course modules and instructional help in subjects including: Biology, Chemistry, Physics, Mathematics, Computer Science, Economics, Drama, Film, Philosophy, and Psychology, as well as more subjects.