The output of shopt -p can be of some help here. It prints a list of settable options. Sadly, on Lion, autocd is not one of them (see excerpt below).
Edit Lauri's answer aboveLauri's answer above has a solution for updating your shell to include autocd
$ shopt -p
shopt -u cdable_vars
shopt -u cdspell
shopt -u checkhash
shopt -s checkwinsize
shopt -s cmdhist
shopt -u compat31
shopt -u dotglob
shopt -u execfail
shopt -s expand_aliases
shopt -u extdebug
shopt -u extglob
shopt -s extquote
shopt -u failglob
shopt -s force_fignore
shopt -u gnu_errfmt
shopt -u histappend
shopt -u histreedit
shopt -u histverify
shopt -s hostcomplete
shopt -u huponexit
shopt -s interactive_comments
shopt -u lithist
shopt -s login_shell
shopt -u mailwarn
shopt -u no_empty_cmd_completion
shopt -u nocaseglob
shopt -u nocasematch
shopt -u nullglob
shopt -s progcomp
shopt -s promptvars
shopt -u restricted_shell
shopt -u shift_verbose
shopt -s sourcepath
shopt -u xpg_echo
