I'm currently building this out on my webmaster site that will be launching late next month or November :P For the first stage, signup links will pre-pop forms based on your registration information... It's a lot of work as each affiliate is different so it won't be available for all sponsors off the bat but it's a work in progress... Eventually I'd like to auto join and parse all relevant information back to the user in a standardized format. That way you could put checks in the box for each sponsor you're interested in and hit "Sign up for these sites"...
I'll post a link when it's all up and running
EDIT: Of course it will only work for the first page of signups which drastically vary but... it's a step in the right direction. I'm also implementing an API for callback routines where sponsors can request registration information for a new webmaster if they provide the user_id and a security token/hash which is generated based on the site requesting and the webmaster requesting.