This is the best resource I've used for higher level math. I'm not sure why more people don't know about it because everything is VERY in depth with great examples and explanations.
I've used Paul's Online Notes for all my higher level math classes starting from Calculus 2. It has been more useful to me, even more than Khan's Academy. I like the little tricks and mnemonics that he teaches, especially in Linear Algebra. Example here: http://tutorial.math.lamar.edu/Classes/LinAlg/DeterminantRev.... Much easier way of calculating determinants.
Another resource I've used is Patrick JMT's excellent videos found at: http://patrickjmt.com. He really goes over problems slowly. Best math teacher I've ever had.
http://tutorial.math.lamar.edu/Classes/LinAlg/LinAlg.aspx