digital-tutors has a short-but-sweet Maxwell section, but of course it’s a paid site; probably only worth it if you already have a membership.
Next Limit’s own YouTube channel also has an exhaustive selection of videos, that are more explanatory than they are “step-by-step.” http://www.youtube.com/playlist?list=PL1FE393A926FF8A17
But overall that series by James Coleman is the gold standard…
Otherwise just visit their forums and scour for weeks on end.
www.maxwellrender.com/forum