DS brought home log-in info from his school for Adapted Mind Math and so far I like it better than ixl. With ixl they have to do a ridiculous number of problems before they finish a lesson, but with Adapted Mind Math it "adapts" the number of problems based on whether they are answering correctly or not and they may only have to do 5 or 10 problems for a standard before mastering it. There are also video lessons on Adapted Mind, which ixl doesn't have. It's about the same cost as ixl. I think it only goes through grade 5 or 6 standards.
DD really likes Khan Academy, which goes from around grade 3 to very advanced math (and best of all it is FREE).
I don't know that I would classify either of those sites as "fun". With both of them kids can earn badges which my kids enjoy (7 and 8 yo).
DS really liked Dreambox (we did a free trial), but I'm not sure how closely it aligns with standards.
