Brad Raymond is a wonderful baritone gone tenor who is enjoying a promising national and international career as an opera singer. Since he has made the transition from baritone to tenor, he's had to deal with the issues of the passaggio extensively.  He has some great tips on how to deal with the transitions between registers.  You can find him on the web at http://www.bradraymondtenor.com/   Freya's Blog with great singing tips: http://www.freyas-singing-tips.com/