That Christophe guy over at Path to SharePoint never rests! I just spotted his post on his new Easy Tabs Web Part. I haven’t dug under the covers on it yet, but Christophe’s stuff is always nice.
The Easy Tabs Web Part is a Content Editor Web Part with some JavaScript. When added to a Web Part zone, the script identifies all the Web Parts that are present in the zone. For each visible Web Part it creates a tab named after the Web Part title.
The look and feel of the tabs match the theme of the site.
UPDATE 2009-05-26: I did some fiddling with this today, and it is really slick, and so elegant in its simplicity!