If you are looking for more features in the builtin forum webpart in in SharePoint you may want to look at thoses alternatives :
- Tobias Zimmergren's SharePoint Forums WebPart
- SharePoint Forums Web Part Project
- Enhanced Discussion Board Edition from The Community Kit for SharePoint Project
- KWizCom SharePoint Forum Web Part (commercial)
Note : I didn't try any of those webparts (you'll have to try them for yourself), some are still in beta and there may be more Forums WebPart on the net.