I am gonna start using zsh as my default shell. Here is how you make it your default shell for Terminal.
 
http://blog.gwikzone.org/2006/09/06/mac-os-x-properly-change-shell-when-using-zsh-from-darwinports-macports

The last line in that post is incorrect.  This is what the last line should be:

chsh -s /opt/local/bin/zsh