Are you looking for credits to complete your certification?  This post is a summary of a discussion that took place on OPHUN-L, a listserv for physics teachers.

American Museum of Natural History

University of Virgina

North Carolina State (Matter and Interactions)

For actually learning physics content nothing beats hands-on, student centered, discourse-intensive  experiences for physics teachers led by master teachers, so do consider a summer modeling course as well:

Arizona State U.

Buffalo State

SUNY Learning Network

Multiple universities (including Montana State — highly recommended by others)