(compiled for a teacher friend who is in the process of planning a sabbatical)
Before:
http://lindarzoska.wordpress.com/category/sabbatical-proposal/
http://davidwarlick.com/2cents/?p=405
http://www.projectmojave.com/blog/how-to-take-a-sabbatical-an-author-interview-with-dan-clements/
During:
After:
http://onescoopofmeatplease.blogspot.com/2008/02/repressed-anxiety-bags-of-misery.html
Beaver Country Day School has an established sabbatical policy:
http://www.bcdschool.org/podium/default.aspx?t=111614&rc=0
(Might be fun to track down some of the folks who have returned from sabbaticals...)