There is currently functionaility to create different sites:
Each can have its own branding once logged in but not prior to logging in due to only 1 branded login page being setup so rather limiting the usage of multiple branded sites, these additonal VF pages needs to be developed seperately.
It would be good if a seperate site can be created that also has the option to create the same branded login page so:
company.force.com/site1 has site1 branded login page
company.force.com/site2 has site2 branded login page
company.force.com/site3 has site3 branded login page