By default the new project template for ASP.NET MVC 3 adds the following to the default layout (masterpage in razor):
@ViewBag.Title
<
I would say that as long as it's only the Title you want to set, it's ok to use the ViewBag. Well, maybe not only - at most 2-3 properties.
But if you start to see you're setting more and more (common) properties in every controller action, I would go with a strongly typed "ViewModelBase class". But it's just me.