Many of the Dreamforce breakout sessions are recorded and posted on Youtube. Here are some of ones I found most interesting.
Dreamforce 2009 – The process for getting Salesforce.com Certified is discussed. Sample questions and tips on test taking strategy are also mentioned. It focuses mostly on Certified Administrator but it applies to the other exams also.
Making Easy-to-Use User Interfaces with Force.com
Dreamforce 2011 – Some of the best advice on creating click-to-configure user interfaces. I especially like that it starts with core principles and then provides many examples.