The EntLib Extensions to WSSF have gotten more and more attention lately. There now is a (very positive) announcement about the extensions on the WSSF site, and there is a complete article on MSDN explaining how to use the extensions. Check it out!

Links:
EntLib Extensions to WSSF: http://www.codeplex.com/EntLibExtensionsWSSF
MSDN article: http://msdn.microsoft.com/en-us/magazine/cc164250.aspx
WSSF site: http://www.codeplex.com/servicefactory