I’ve bought all of the training DVD’s and projects and I think I learned the most from Andy’s DVD
http://www.blender3d.org/e-shop/product_info_n.php?products_id=105
and secondly I learned a lot from Pablos DVD:
http://www.blender3d.org/e-shop/product_info_n.php?products_id=118
Andy’s Creature factory steps you through the creation of an epic project whereas Pablos is a collection of shorter movies demonstrating how to use smaller features within blender. Both videos are for 2.49, but directly relate to the toolsets in 2.5 - the tools are just in different places now, but work very similarly. Both DVD’s include all of the source files so if there is something crazy you are trying to figure out, you can just look at the blends.
As an example, these character are all on Pablo’s DVD (Hell, you can download some of the blends on his site):
http://www.venomgfx.com.ar/characters/
I think there will be plenty of learning from Sintel, but the focus tends to be on the movie instead of the learning on the Open Projects - once you are up to speed you could probably look at the source files and see what is going on, but you would need to know the basics first.