Maybe visiting a site would locally select the appropriate group that site was assigned to. For example, going to gmail.com would automatically use the "Google"

Maybe visiting a site would locally select the appropriate group that site was assigned to. For example, going to gmail.com would automatically use the "Google" Group. If a site is assigned to multiple groups, prompt the user to select a group. An unassigned site would use a default group, or create its own group for return visits, or create a temporary group.