<!DOCTYPE html>
<html ng-app="app">

  <head>
    <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.2.19/angular.js"></script>
    <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.2.19/angular-sanitize.js"></script>
    <script src="script.js"></script>
  </head>

  <body ng-controller="PruebaController">
    <div>{{mensaje}}</div>
    <div ng-bind="mensaje"></div>    
    <div ng-bind-html="mensaje"></div>   
    <div ng-non-bindable>{{mensaje}}</div>    
  </body>

</html>
var app = angular.module("app", ['ngSanitize']);

app.controller("PruebaController", function($scope) {
  $scope.mensaje = "Hola <strong>Mundo</strong>";
});
Ejemplos de directivas: ng-bind, ng-bind-html y ng-non-bindable