Single user login
I intend to develop a site using WP
Multisite where I plan to install a Jobroller a Clipper and a ClassiPress in sub sites. That means I would have something like; mysite.com and sub sites like mysite.com/ jobroller and mysite.com/ClassiPress.
The question I have is how I can do to have a single user login that permit him to freely access to posting jobs, classifieds or coupons without having to login into each of the single sub sites.