I've extended the earlier VCS-friendly shell prompt to add support for Mercurial and you can now get my current .bash_profile from GitHub:

__has_parent_dir () {
    # Utility function so we can test for things like .git/.hg without firing
    # up a separate process
    test -d "$1" && return 0;

    current="."
    while [ ! "$current" -ef "$current/.." ]; do 
        if [ -d "$current/$1" ]; then
            return 0;
        fi
        current="$current/..";
    done

    return 1;
}

__vcs_name() {
  if [ -d .svn ]; then 
    echo " [svn]"; 
  elif [ -d RCS ];  then 
    echo " [RCS]";  
    elif __has_parent_dir ".git"; then
        echo "$(__git_ps1 ' [git %s]')";
    elif __has_parent_dir ".hg"; then
        echo " [hg $(hg branch)]"
  fi
}

PS1='\[\033]0;\u@\h:\w\007\]\u@\h:\w$(__vcs_name) $ '