authenticating users between websites

[Dan Langille]

I'm getting this request often and I'm not sure how to solve it.  A 
client will have two websites and wants users to be able to browse 
freely between the websites after having logged into the primary 
website.

For example, I browse to a.example.org, log in, and continue 
browsing.  Then I browse over to b.example.org.... How can I be 
automagically be authenticated on that other website?

cheers
-- 
Dan Langille : http://www.langille.org/
BSDCan - The Technical BSD Conference - http://www.bsdcan.org/