Maintaining session data across multiple domains

I'm working on an application that can be accessed from multiple domains. I want to maintain session data across these domains, such that if a user logs in at www.domain1.com, then moves to www.domain2.com, they will still be logged in with the same account. Is this possible in Rails? Could anyone point me towards a guide of how to achieve it?

Many thanks, Adam

I'm working on an application that can be accessed from multiple domains. I want to maintain session data across these domains, such that if a user logs in at www.domain1.com, then moves to www.domain2.com , they will still be logged in with the same account. Is this possible in Rails? Could anyone point me towards a guide of how to achieve it?

Well you will definitely need to move away from the cookie store. I imagine you could do something like redirect users with no session
to blah.domain.com - this creates/looks up their session id. Then it
redirects them back to the original domain along with a token telling
that app what the session id of the user should be (so that this app
can set the cookie saying what the session id is)

Fred