Exchange public folders are not dead. There are still a lot of uses for them. For instance, it is a great way for a team to have a place to collect email by using drag and drop. You can have "favorite" public folders that are easy to locate if your company has a large public folder collection. You can use LookOut to search them. They can use all of the great views the Outlook affords. They can be mail enabled, etc., etc.
Many of the usage scenarios that are afforded by SharePoint Portal Server and Windows SharePoint Services align well with the previously mentioned scenarios in Exchange. The problem has been creating a consolidated view of all of the stuff in your project. You might want to have structured issue tracking and document history stored in SharePoint but have unstructured conversation histories or a distribution list archive in Exchange. You have always been able to use a Page Viewer Web Part, but as Mads noted, it hasn't always been elegant.
Well, I was trying to explore how to expose Exchange 2003 public folder with XML so that I could have my RSS feeds and public folder history right next to each other in Data Viewer Web Parts, but I stumbled upon a more elegant simpler solution: part=1.
If you use the following URL format:
as the URL of your page within the page viewer web part you get a nicely formatted view of the contents of the folder that doesn't cause the page to scroll on load and looks quite nice within a web part page. It still sports all of the rich client functionality of Outlook Web Access (OWA).