Other than the sites typhoon has listed and www.CADclips.com as coreed has mentioned for great 'video tutorials' you should also keep tabs on the various REVIT blogs such as: www.revitoped.com www.reviteer.com htp://revitrants.blogspot.com/  http://www.caddigest.com/subjects/revit/tutorials.htm  http://revitbeginners.blogspot.com/ 

The first thing you need to understand about REVIT as apposed to AutoCAD or ADT/ACA is pretty much everything modeled is tied to a 'level' and it's all parametric. Change a number or dimension and the model updates.You can move the levels up and down and the model updates. You can constrain 'walls' 'roofs' etc. to start and stop (constrain) in relation to these levels. Most 'objects' in REVIT are part of what has been defined as a 'family'. Families are like 'blocks' x 1000. Better than dynamic blocks. Some families are 'system families'. The are special. Walls, doors, windows, furniture, symbols, annotations . . .they are all 'families'. Once you get going with REVIT you will soon want to create your own custom families to suite your particular needs. This is where you want to watch the www.CADclips.com  videos and /or  visit with some of these other blogs (which list more blogs etc.) to advance your skills.

The site www.revitcity.com is the first place to look for custom families because we all upload them here and they are free to download.

Good luck, there's nothing like the look of someones face when they start to see the power of REVIT.