I'd tend to agree with Aidus about the user manual. There's a Maxwell manual that's a couple hundred pages w/ an index and a SU plugin manual that's probably 20ish pages. Other than that I don't know of any really great tutorials to take you through all of the basics of the program (the Think website that Stinkie gave has some good individual tutorials though).
The good thing, though, in my opinion is Maxwell has done a good job of avoiding the typical rendering language that can get a bit complicated. Most of the settings tie back to real life science and physics so if you need to know what something is it's usually pretty easy to find out. Instead of relying on one sentence to tell you what a particular camera function is and does, you get endless sites which can explain what a diaphram is, differences between apertures, focal distances, etc. I find it pretty intuative in that sense.
When it comes to material creation, there's some technical stuff but the manual is quite good at explaining those aspects. Often times you can get by w/o having to know too much about the more complex settings by using the default materials and changing the maps or downloading materials from the maxwell website.
-Brodie
