UPDATE: SharePoint Designer 2010 Beta has been released! Get it here...
Recently I was tasked with setting up a custom themed SharePoint portal to do a blog & news letter for a project I am involved with at work. It looks like the place to start is SharePoint designer. I plan to post on my progress as I work with this tool.
From Microsoft....
SHAREPOINT DESIGNER 2007 IS NOW FREE! Learn more about these changes and future direction. Watch the Q&A video to learn more.
Office SharePoint Designer 2007 provides the powerful tools you need to deliver compelling and attractive SharePoint sites and quickly build workflow-enabled applications and reporting tools on the SharePoint platform, all in an IT-managed environment.