Although WSSv3 supports workflow on libraries and list, SharePoint Designer is required to build the workflow.  A MOSS 2007 Team Site, on the other hand, provides a browser based interface for the list/library manager to build a workflow.  MOSS 2007 provides a number of workflows available to any list/library in the site collection.

The following screen shots show the workflow activities are configured through the web interface.

You can still use SharePoint Designer to build and configure worflows on a MOSS 2007 server.

I'll get back to purely WSS posts once I get this MOSS coolness out of my system, promise.