The people to follow are not a representative choice but those I know and who have a good web presence. If you want to be listed here drop me a mail.
Ali Arsanjani does research on rules and rule systems and has also been the organizer of an OOPSLA 2000 Workshop on Business Rules
Jens Coldewey: does consulting on product servers
Ralph Johnson used to be interested in building insurance software, mostly using Smalltalk. He still does useful stuff for the domain, e.g. the Accounts framework and also the User Defined Products framework. He did this work together with Jeff Oakes.
Wolfgang Keller: operates this site and is an architect at AMB Generali Informatik
Joe Yoder (who also does database access layers) is another organizer of the OOPSLA workshop on Business Rules
Lubor Sesera from softec Bratislava has also written patterns in the insurance domain (Recurring Duties Analysis Pattern)