That's a very broad question!
Answers could range from LLD for dummies to MIT has a highly esteemed graduate HLD course.
Further, these forums aren't as focused on broad learning as possibly others are.
So, recommend you also provide the scope for the kind of course your looking for and also consider the purpose of a particular web site and its sections.
BTW, I'm not trying to say you cannot obtain very good advice here, instead I'm trying to insure you do get excellent suggestions.
