I have just released the “Easy Tabs Web Part” for SharePoint 2007. Check out the demo, the video and the Web Part for download on my SharePoint site:
The Web Part can be used on a SharePoint 2007 site by anybody who has design or full control permissions (it is actually based on a Content Editor Web Part). The installation does not require server access.
Update [5/26/2009] Thanks all for the great feedback (comments and e-mails)!
I have added a twin Web Part to the download section, for those who want another set of tabs for another Web Part zone on the same page.
I am also going to add two sections on the site, one for FAQ and another to track known issues.
Update [5/29/2009] Version 2 now includes cookies. Reloaded pages will remember the active tab. This is useful for example when you switch between different views of a calendar (Mark’s comment), or if you use sorting/filtering options on list columns.