<p>Art of problem solving is a another good source for additional topics in math: [Online</a> Math Classes](<a href=“http://www.artofproblemsolving.com/Classes/AoPS_C_Enroll.php]Online”>http://www.artofproblemsolving.com/Classes/AoPS_C_Enroll.php)</p>
<p>But looks like some of the traditional topics (like Algebra), are taught online during school year, not summer.</p>