I have set my terminal preferences to execute:
set -o vi
at startup. The problem is I don't get that command executed when open a new terminal tab.
Is there something like .profile in OS X where I can put that command?
Because, as noted, Terminal has used bash by default for a few versions, you may want to keep an eye out for a .bash_profile file if .profile isn't present. See the "which startup files are read by the shell?" FAQ at http://hayne.net/MacDev/Notes/unixFAQ.html#shellStartup which explain how the different files are used and the order in which they're read at startup.