"Many of you have used the "Fabulous 40 templates" that were created for Windows SharePoint Services 3.0. Some of these templates were created as site admin templates (.stp files) and some as server admin templates (.wsp files). Microsoft is not releasing new versions of these templates for SharePoint 2010 Products."
"Sites based on these templates should upgrade, but you'll want to try out your upgrade in a test environment before you upgrade your production environment so that you can catch any potential issues. Definitely use the pre-upgrade checker to identify any issues (some people have seen problems with custom workflows or CAML-based views in the templates). However, after upgrade, you won't be able to use STP files to create new templates."
more:
http://www.techsolutions.net/Blog/tabid/65/EntryId/17/Fab-40-Templates-for-MOSS-2010.aspx
http://www.techsolutions.net/Blog/tabid/65/EntryId/18/Fab-40-for-Sharepoint-Foundation.aspx