<p>How would you reccommend handling RSS Feeds in ASP.NET MVC?  Using a third party library?  Using the RSS stuff in the BCL?  Just making an RSS view that renders the XML?  Or something completely different?</p>

Here is what I recommend:
Create a class called RssResult that
inherits off the abstract base class
ActionResult.
Override the ExecuteResult method.
ExecuteResult has the ControllerContext passed to it by the caller and with this you can get the data and content type.
Once you change the content type to rss, you will want to serialize the data to RSS (using your own code or another library) and write to the response.
Create an action on a controller that you want to return rss and set the return type as RssResult.  Grab the data from your model based on what you want to return.
Then any request to this action will receive rss of whatever data you choose.
That is probably the quickest and reusable way of returning rss has a response to a request in ASP.NET MVC.