I don't have any recommendations for resources, but there are some good books and probably videos out there.
I learned to use Inventor from someone who works with it. Coming from a strong AutoCAD (and simply CAD) background helped, but it's not the same. I dabble in Inventor, not an expert by any means, but enough to be dangerous.
As JNieman mentioned, when modelling in AutoCAD, you're creating shapes, using extrusions, lofts, slices, etc... but they are dumb objects when your done.
In Inventor, you create each part separately using some the same techniques, but with sketches. Each feature you add to a part starts with a sketch that you extrude, or revolve or whatever. What's nice is you can go back in and edit the sketch which will change the part (you can't do that in Acad!) Plus, you can choose/add properties to these objects, which makes them smart.
Then you create Assemblies, which is simply bringing in parts and constraining them with the correct constraints. You can even create sub-assemblies and bring those into assemblies.
Also, back to parts; you can add features such as holes, fillets, chamfers etc to a part with out having it be part of the initial part sketch. Threaded holes for instance are best created (IMO) by placing points in a sketch, and then simply creating hole features on those points. Then when annotating them on a sheet, it "knows" what the hole is and notes it properly.
To sum it up, learning 3D autocad will help you understand creating 3D obects with basic methods like extrude, revolve, etc with 2D line work (similar to the "sketch" in inventor) as well as thinking in 3D, but that's about as far as the similarities go.
That's my two cents anyway (more like $1.25)