There are tons of video tutorials out there, and there is a general problem with them: You dont really know if they are good or not, or if they touch the problem you seek a solution for - until you actually watched it. As many of them are 15min+ long, some go even in areas of an hour, I thought I share my bookmark folder with you, where I collect the ones I have watched myself and so can say out of first hand that they are definitely not a waste of time.

No special sorting, and feel free to add your own ones.

http://vimeo.com/2158706 (Artifacts: Why triangles are bad and how to get good subsurf results)

http://www.blenderguru.com/videos/introduction-to-rigging

http://www.luceri.it/2010/06/microtutorial-n°1/ (Control loopflow - after the model is done, awesome little trick) 

http://cgcookie.com/blender/2011/09/14/tip-using-multiple-uv-coordinates/

http://cgcookie.com/blender/2011/08/08/retopology-with-the-bsurfaces-add... (refers to version 1.5 what is not GPL'ed yet at time of writing this)

http://www.cgarena.com/freestuff/tutorials/misc/aircraft/modeling.html (oldschool html-Tutorial) 

http://vimeo.com/14560538 (retopology with the snapping tool)